Be able to compile nanobench for Chromecast

Be able to compile nanobench for Chromecast

Get toolchain from https://goto.google.com/ncoqy and put in
$CAST_TOOLCHAIN

gn gen out/chromecast --args='cc="$CAST_TOOLCHAIN/armv7a/bin/armv7a-cros-linux-gnueabi-gcc" cxx="$CAST_TOOLCHAIN/armv7a/bin/armv7a-cros-linux-gnueabi-g++" ar="$CAST_TOOLCHAIN/armv7a/bin/armv7a-cros-linux-gnueabi-ar" is_official_build=true skia_use_fontconfig=false extra_ldflags=["-static-libstdc++","-static-libgcc"] target_cpu="arm" skia_enable_gpu=false skia_use_system_freetype2=false'

ninja -C out/chromecast nanobench

We go with is_official_build to minimize binary size, as the chromecast
does not have much onboard storage.

They do not package libstdc++ so we add the link options:
-static-libstdc++ -static-libgcc

-momit-leaf-frame-pointer is not supported, so we delete it, as it is not important.

BUG=skia:

Change-Id: I7b0882ab5d6109f07345a2d59df265efef9b9554
Reviewed-on: https://skia-review.googlesource.com/9338
Commit-Queue: Kevin Lubick <kjlubick@google.com>
Reviewed-by: Mike Klein <mtklein@chromium.org>