Fix timer on android build.

Set CMAKE_SYSTEM_NAME to android in toolchain cmake file.
Add Android to CONFIG_OS_SUPPORT.

Change-Id: Ib1a9a2fca794d0b91247ed9c64f7bef379ee2aa2
diff --git a/build/cmake/aom_configure.cmake b/build/cmake/aom_configure.cmake
index f84e39c..1cdff63 100644
--- a/build/cmake/aom_configure.cmake
+++ b/build/cmake/aom_configure.cmake
@@ -176,7 +176,7 @@
   require_compiler_flag("-pg" YES)
 endif()
 
-if("${AOM_TARGET_SYSTEM}" MATCHES "Darwin\|Linux\|Windows")
+if("${AOM_TARGET_SYSTEM}" MATCHES "Darwin\|Linux\|Windows\|Android")
   set(CONFIG_OS_SUPPORT 1)
 endif()
 
diff --git a/build/cmake/toolchains/arm64-android-clang.cmake b/build/cmake/toolchains/arm64-android-clang.cmake
index 28b9ae5..5e20baf 100644
--- a/build/cmake/toolchains/arm64-android-clang.cmake
+++ b/build/cmake/toolchains/arm64-android-clang.cmake
@@ -44,3 +44,5 @@
 
 # No runtime cpu detect for arm64-android-clang.
 set(CONFIG_RUNTIME_CPU_DETECT 0 CACHE NUMBER "")
+
+set(CMAKE_SYSTEM_NAME "Android")