Build libmonochrome.so with secondary toolchain

build/toolchain/android/BUILD.gn

Index: build/toolchain/android/BUILD.gn
diff --git a/build/toolchain/android/BUILD.gn b/build/toolchain/android/BUILD.gn
index 4a1a29f7eef579b3f97f4c45e397d7966ae05b6a..f0ef413e93f006808744a20cdb8deea4cf4fb6ae 100644
--- a/build/toolchain/android/BUILD.gn
+++ b/build/toolchain/android/BUILD.gn
@@ -59,6 +59,10 @@ template("android_gcc_toolchain") {
     # Don't use .cr.so for loadable_modules since they are always loaded via
     # absolute path.
     loadable_module_extension = ".so"
+
+    if (defined(invoker.v8_toolchain_cpu)) {
+      v8_toolchain_cpu = invoker.v8_toolchain_cpu
+    }
   }
 }
 
@@ -73,28 +77,61 @@ template("android_gcc_toolchains_helper") {
   }
 }
 
-android_gcc_toolchains_helper("x86") {
-  toolchain_cpu = "x86"
-  toolchain_root = x86_android_toolchain_root
-  sysroot = "$android_ndk_root/$x86_android_sysroot_subdir"
-  lib_dir = "usr/lib"
-  binary_prefix = "i686-linux-android"
+template("android_gcc_toolchains_x86_helper") {
+  android_gcc_toolchains_helper(target_name) {
+    toolchain_cpu = "x86"
+    toolchain_root = x86_android_toolchain_root
+    sysroot = "$android_ndk_root/$x86_android_sysroot_subdir"
+    lib_dir = "usr/lib"
+    binary_prefix = "i686-linux-android"
+    forward_variables_from(invoker, "*")
+  }
 }
 
-android_gcc_toolchains_helper("arm") {
-  toolchain_cpu = "arm"
-  toolchain_root = arm_android_toolchain_root
-  sysroot = "$android_ndk_root/$arm_android_sysroot_subdir"
-  lib_dir = "usr/lib"
-  binary_prefix = "arm-linux-androideabi"
+template("android_gcc_toolchains_arm_helper") {
+  android_gcc_toolchains_helper(target_name) {
+    toolchain_cpu = "arm"
+    toolchain_root = arm_android_toolchain_root
+    sysroot = "$android_ndk_root/$arm_android_sysroot_subdir"
+    lib_dir = "usr/lib"
+    binary_prefix = "arm-linux-androideabi"
+    forward_variables_from(invoker, "*")
+  }
 }
 
-android_gcc_toolchains_helper("mipsel") {
-  toolchain_cpu = "mipsel"
-  toolchain_root = mips_android_toolchain_root
-  sysroot = "$android_ndk_root/$mips_android_sysroot_subdir"
-  lib_dir = "usr/lib"
-  binary_prefix = "mipsel-linux-android"
+template("android_gcc_toolchains_mipsel_helper") {
+  android_gcc_toolchains_helper(target_name) {
+    toolchain_cpu = "mipsel"
+    toolchain_root = mips_android_toolchain_root
+    sysroot = "$android_ndk_root/$mips_android_sysroot_subdir"
+    lib_dir = "usr/lib"
+    binary_prefix = "mipsel-linux-android"
+    forward_variables_from(invoker, "*")
+  }
+}
+
+android_gcc_toolchains_x86_helper("x86") {
+}
+
+android_gcc_toolchains_arm_helper("arm") {
+}
+
+android_gcc_toolchains_arm_helper("mipsel") {
+}
+
+# The below toolchains which ends with _v8_foo are the secondary
+# toolchains, they define the platform v8 snapshot should be
+# built for.
+android_gcc_toolchains_arm_helper("arm_v8_arm") {
+  v8_toolchain_cpu = "arm"

[agrieve, 2016/07/21 16:57:46]

Just one more question the comment doesn't yet answer: Why is "arm" not already
the default when current_cpu = arm? (should say what would happen if we didn't
set this explicitly here)

[Dirk Pranke, 2016/07/21 17:15:26]

Right, this shouldn't be needed.

[michaelbai, 2016/07/21 17:58:05]

Dirk, could you clarify what shouldn't be needed?

[Dirk Pranke, 2016/07/21 18:31:56]

v8_toolchain_cpu will match toolchain_cpu by default, so you don't need to
define these toolchains; they will have the same effect as the ones on lines
113-120.

[michaelbai, 2016/07/21 19:21:08]

How could I miss that part! but I remember it didn't work at the first time I
tried your v8 patch; the good news is this patch become very simple.

+}
+
+android_gcc_toolchains_arm_helper("mipsel_v8_mipsel") {
+  v8_toolchain_cpu = "mipsel"
+}
+
+android_gcc_toolchains_arm_helper("x86_v8_x86") {
+  v8_toolchain_cpu = "x86"
 }
 
 android_gcc_toolchains_helper("x64") {