Build gtest from source rather than using SDK-provided version

ports/libyuv/nacl.patch

Index: ports/libyuv/nacl.patch
diff --git a/ports/libyuv/nacl.patch b/ports/libyuv/nacl.patch
index d5b03b130a77835899ad56d67c29a51a10660c4c..890a2a9e6ac34c1d0955482dc2ecb88333b6bfe1 100644
--- a/ports/libyuv/nacl.patch
+++ b/ports/libyuv/nacl.patch
@@ -1,24 +1,18 @@
 diff --git a/CMakeLists.txt b/CMakeLists.txt
 --- a/CMakeLists.txt
 +++ b/CMakeLists.txt
-@@ -100,19 +100,7 @@ if (JPEG_FOUND)
- endif()
- 
+@@ -102,12 +102,13 @@ endif()
  if(TEST)
--  find_library(GTEST_LIBRARY gtest)
--  if(GTEST_LIBRARY STREQUAL "GTEST_LIBRARY-NOTFOUND")
+   find_library(GTEST_LIBRARY gtest)
+   if(GTEST_LIBRARY STREQUAL "GTEST_LIBRARY-NOTFOUND")
 -    set(GTEST_SRC_DIR /usr/src/gtest)
--    if(EXISTS ${GTEST_SRC_DIR}/src/gtest-all.cc)
--      message(STATUS "building gtest from sources in ${GTEST_SRC_DIR}")
--      set(gtest_sources ${GTEST_SRC_DIR}/src/gtest-all.cc)
--      add_library(gtest STATIC ${gtest_sources})
--      include_directories(${GTEST_SRC_DIR})
--      set(GTEST_LIBRARY gtest)
--    else()
--      message(FATAL_ERROR "TEST is set but unable to find gtest library")
--    endif()
--  endif()
-+  set(GTEST_LIBRARY gtest)
- 
-   add_executable(libyuv_unittest ${ly_unittest_sources})
-   target_link_libraries(libyuv_unittest ${ly_lib_name} ${GTEST_LIBRARY} pthread)
++    set(GTEST_SRC_DIR /usr/src/gtest CACHE STRING "Location of gtest sources")
+     if(EXISTS ${GTEST_SRC_DIR}/src/gtest-all.cc)
+       message(STATUS "building gtest from sources in ${GTEST_SRC_DIR}")
+       set(gtest_sources ${GTEST_SRC_DIR}/src/gtest-all.cc)
+       add_library(gtest STATIC ${gtest_sources})
+       include_directories(${GTEST_SRC_DIR})
++      include_directories(${GTEST_SRC_DIR}/include)
+       set(GTEST_LIBRARY gtest)
+     else()
+       message(FATAL_ERROR "TEST is set but unable to find gtest library")