Merge pull request taka-no-me#46 from OSVR/use-gcc-ar-when-possible

If there is gcc-ar for the desired toolchain, use it.

Author: Andrey Kamaev

android.toolchain.cmake

@@ -1098,7 +1098,12 @@ if( NOT CMAKE_C_COMPILER )
  endif()
  set( CMAKE_ASM_COMPILER "${ANDROID_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_MACHINE_NAME}-gcc${TOOL_OS_SUFFIX}"     CACHE PATH "assembler" )
  set( CMAKE_STRIP        "${ANDROID_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_MACHINE_NAME}-strip${TOOL_OS_SUFFIX}"   CACHE PATH "strip" )
- set( CMAKE_AR           "${ANDROID_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_MACHINE_NAME}-ar${TOOL_OS_SUFFIX}"      CACHE PATH "archive" )
+ if( EXISTS "${ANDROID_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_MACHINE_NAME}-gcc-ar${TOOL_OS_SUFFIX}" )
+  # Use gcc-ar if we have it for better LTO support.
+  set( CMAKE_AR           "${ANDROID_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_MACHINE_NAME}-gcc-ar${TOOL_OS_SUFFIX}"      CACHE PATH "archive" )
+ else()
+  set( CMAKE_AR           "${ANDROID_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_MACHINE_NAME}-ar${TOOL_OS_SUFFIX}"      CACHE PATH "archive" )
+ endif()
  set( CMAKE_LINKER       "${ANDROID_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_MACHINE_NAME}-ld${TOOL_OS_SUFFIX}"      CACHE PATH "linker" )
  set( CMAKE_NM           "${ANDROID_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_MACHINE_NAME}-nm${TOOL_OS_SUFFIX}"      CACHE PATH "nm" )
  set( CMAKE_OBJCOPY      "${ANDROID_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_MACHINE_NAME}-objcopy${TOOL_OS_SUFFIX}" CACHE PATH "objcopy" )