document GN for ios

docs/getting_started.md

 # Getting Started
 
 How to get and build the libyuv code.
 
 ## Pre-requisites
 
 You'll need to have depot tools installed: https://www.chromium.org/developers/how-tos/install-depot-tools
 Refer to chromium instructions for each platform for other prerequisites.
 
 ## Getting the Code
@@ skipping 54 matching lines @@
 
     git clone https://chromium.googlesource.com/libyuv/libyuv
 
 
 ## Building the Library and Unittests
 
 ### Windows
 
     call gn gen out/Release "--args=is_debug=false target_cpu=\"x86\""
     call gn gen out/Debug "--args=is_debug=true target_cpu=\"x86\""
-    ninja -j7 -v -C out/Release
-    ninja -j7 -v -C out/Debug
+    ninja -v -C out/Release
+    ninja -v -C out/Debug
 
     call gn gen out/Release "--args=is_debug=false target_cpu=\"x64\""
     call gn gen out/Debug "--args=is_debug=true target_cpu=\"x64\""
-    ninja -j7 -v -C out/Release
-    ninja -j7 -v -C out/Debug
+    ninja -v -C out/Release
+    ninja -v -C out/Debug
 
 #### Building with clang-cl
 
     set GYP_DEFINES=clang=1 target_arch=ia32
     call python tools\clang\scripts\update.py
 
     call gn gen out/Release "--args=is_debug=false is_official_build=false is_clang=true target_cpu=\"x86\""
     call gn gen out/Debug "--args=is_debug=true is_official_build=false is_clang=true target_cpu=\"x86\""
-    ninja -j7 -v -C out/Release
-    ninja -j7 -v -C out/Debug
+    ninja -v -C out/Release
+    ninja -v -C out/Debug
 
     call gn gen out/Release "--args=is_debug=false is_official_build=false is_clang=true target_cpu=\"x64\""
     call gn gen out/Debug "--args=is_debug=true is_official_build=false is_clang=true target_cpu=\"x64\""
-    ninja -j7 -v -C out/Release
-    ninja -j7 -v -C out/Debug
+    ninja -v -C out/Release
+    ninja -v -C out/Debug
 
 ### macOS and Linux
 
     gn gen out/Release "--args=is_debug=false"
     gn gen out/Debug "--args=is_debug=true"
-    ninja -j7 -v -C out/Release
-    ninja -j7 -v -C out/Debug
+    ninja -v -C out/Release
+    ninja -v -C out/Debug
 
 ### Building Offical with GN
 
     gn gen out/Official "--args=is_debug=false is_official_build=true is_chrome_branded=true"
     ninja -C out/Official
 
 ### iOS
-This section needs an update to GN build documentation.
 http://www.chromium.org/developers/how-tos/build-instructions-ios
 
 Add to .gclient last line: `target_os=['ios'];`
 
-armv7
-
-    GYP_DEFINES="OS=ios target_arch=armv7 target_subarch=arm32" GYP_CROSSCOMPILE=1 GYP_GENERATOR_FLAGS="output_dir=out_ios" ./gyp_libyuv
-    ninja -j7 -C out_ios/Debug-iphoneos libyuv_unittest
-    ninja -j7 -C out_ios/Release-iphoneos libyuv_unittest
-
 arm64
 
-    GYP_DEFINES="OS=ios target_arch=arm64 target_subarch=arm64" GYP_CROSSCOMPILE=1 GYP_GENERATOR_FLAGS="output_dir=out_ios" ./gyp_libyuv
-    ninja -j7 -C out_ios/Debug-iphoneos libyuv_unittest
-    ninja -j7 -C out_ios/Release-iphoneos libyuv_unittest
+    gn gen out/Release "--args=is_debug=false target_os=\"ios\" ios_enable_code_signing=false target_cpu=\"arm64\""
+    gn gen out/Debug "--args=is_debug=true target_os=\"ios\" ios_enable_code_signing=false target_cpu=\"arm64\""
+    ninja -v -C out/Debug libyuv_unittest
+    ninja -v -C out/Release libyuv_unittest
 
-both armv7 and arm64 (fat)
+ios simulator
 
-    GYP_DEFINES="OS=ios target_arch=armv7 target_subarch=both" GYP_CROSSCOMPILE=1 GYP_GENERATOR_FLAGS="output_dir=out_ios" ./gyp_libyuv
-    ninja -j7 -C out_ios/Debug-iphoneos libyuv_unittest
-    ninja -j7 -C out_ios/Release-iphoneos libyuv_unittest
-
-simulator
-
-    GYP_DEFINES="OS=ios target_arch=ia32 target_subarch=arm32" GYP_CROSSCOMPILE=1 GYP_GENERATOR_FLAGS="output_dir=out_sim" ./gyp_libyuv
-    ninja -j7 -C out_sim/Debug-iphonesimulator libyuv_unittest
-    ninja -j7 -C out_sim/Release-iphonesimulator libyuv_unittest
+    gn gen out/Release "--args=is_debug=false target_os=\"ios\" ios_enable_code_signing=false target_cpu=\"x86\""
+    gn gen out/Debug "--args=is_debug=true target_os=\"ios\" ios_enable_code_signing=false target_cpu=\"x86\""
+    ninja -v -C out/Debug libyuv_unittest
+    ninja -v -C out/Release libyuv_unittest
 
 ### Android
 https://code.google.com/p/chromium/wiki/AndroidBuildInstructions
 
 Add to .gclient last line: `target_os=['android'];`
 
 armv7
 
     gn gen out/Release "--args=is_debug=false target_os=\"android\" target_cpu=\"arm\""
     gn gen out/Debug "--args=is_debug=true target_os=\"android\" target_cpu=\"arm\""
-    ninja -j7 -v -C out/Debug libyuv_unittest
-    ninja -j7 -v -C out/Release libyuv_unittest
+    ninja -v -C out/Debug libyuv_unittest
+    ninja -v -C out/Release libyuv_unittest
 
 arm64
 
     gn gen out/Release "--args=is_debug=false target_os=\"android\" target_cpu=\"arm64\""
     gn gen out/Debug "--args=is_debug=true target_os=\"android\" target_cpu=\"arm64\""
-    ninja -j7 -v -C out/Debug libyuv_unittest
-    ninja -j7 -v -C out/Release libyuv_unittest
+    ninja -v -C out/Debug libyuv_unittest
+    ninja -v -C out/Release libyuv_unittest
 
 ia32
 
     gn gen out/Release "--args=is_debug=false target_os=\"android\" target_cpu=\"x86\""
     gn gen out/Debug "--args=is_debug=true target_os=\"android\" target_cpu=\"x86\""
-    ninja -j7 -v -C out/Debug libyuv_unittest
-    ninja -j7 -v -C out/Release libyuv_unittest
+    ninja -v -C out/Debug libyuv_unittest
+    ninja -v -C out/Release libyuv_unittest
 
 mipsel
 
     gn gen out/Release "--args=is_debug=false target_os=\"android\" target_cpu=\"mipsel\" mips_arch_variant=\"r6\" mips_use_msa=true is_component_build=true is_clang=false"
     gn gen out/Debug "--args=is_debug=true target_os=\"android\" target_cpu=\"mipsel\" mips_arch_variant=\"r6\" mips_use_msa=true is_component_build=true is_clang=false"
-    ninja -j7 -v -C out/Debug libyuv_unittest
-    ninja -j7 -v -C out/Release libyuv_unittest
+    ninja -v -C out/Debug libyuv_unittest
+    ninja -v -C out/Release libyuv_unittest
 
     gn gen out/Release "--args=is_debug=false target_os=\"android\" target_cpu=\"mips64el\" mips_arch_variant=\"r6\" mips_use_msa=true is_component_build=true is_clang=false"
     gn gen out/Debug "--args=is_debug=true target_os=\"android\" target_cpu=\"mips64el\" mips_arch_variant=\"r6\" mips_use_msa=true is_component_build=true is_clang=false"
-    ninja -j7 -v -C out/Debug libyuv_unittest
-    ninja -j7 -v -C out/Release libyuv_unittest
+    ninja -v -C out/Debug libyuv_unittest
+    ninja -v -C out/Release libyuv_unittest
 
 arm disassembly:
 
     third_party/android_tools/ndk/toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/bin/aarch64-linux-android-objdump -d ./out/Release/obj/libyuv/row_common.o >row_common.txt
 
     third_party/android_tools/ndk/toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/bin/aarch64-linux-android-objdump -d ./out/Release/obj/libyuv_neon/row_neon.o >row_neon.txt
 
     third_party/android_tools/ndk/toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/bin/aarch64-linux-android-objdump -d ./out/Release/obj/libyuv_neon/row_neon64.o >row_neon64.txt
 
 Running tests:
@@ skipping 14 matching lines @@
     ninja -C out/Debug libyuv_unittest
     ninja -C out/Debug compare
     ninja -C out/Debug convert
     ninja -C out/Debug psnr
     ninja -C out/Debug cpuid
 
 ### ARM Linux
 
     gn gen out/Release "--args=is_debug=false target_cpu=\"arm64\""
     gn gen out/Debug "--args=is_debug=true target_cpu=\"arm64\""
-    ninja -j7 -v -C out/Debug libyuv_unittest
-    ninja -j7 -v -C out/Release libyuv_unittest
+    ninja -v -C out/Debug libyuv_unittest
+    ninja -v -C out/Release libyuv_unittest
 
 ## Building the Library with make
 
 ### Linux
 
-    make -j7 V=1 -f linux.mk
-    make -j7 V=1 -f linux.mk clean
-    make -j7 V=1 -f linux.mk CXX=clang++
+    make V=1 -f linux.mk
+    make V=1 -f linux.mk clean
+    make V=1 -f linux.mk CXX=clang++
 
 ## Building the Library with cmake
 
 Install cmake: http://www.cmake.org/
 
 Default debug build:
 
     mkdir out
     cd out
     cmake ..
@@ skipping 33 matching lines @@
 
 Then run:
 
     c:\intelsde\sde -hsw -- out\Release\libyuv_unittest.exe --gtest_filter=*
 
     ~/intelsde/sde -skx -- out/Release/libyuv_unittest --gtest_filter=**I420ToARGB_Opt
 
 ## Sanitizers
 
     gn gen out/Debug "--args=is_debug=true is_asan=true"
-    ninja -j7 -v -C out/Debug
+    ninja -v -C out/Debug
 
     Sanitizers available: tsan, msan, asan, ubsan, lsan
 
 ### Running Dr Memory memcheck for Windows
 
 Pre-requisite: Install Dr Memory for Windows and add it to your path: http://www.drmemory.org/docs/page_install_windows.html
 
     drmemory out\Debug\libyuv_unittest.exe --gtest_catch_exceptions=0 --gtest_filter=*