Use ANDROID_TOOLCHAIN and ANDROID_TOOLCHAIN_2ND_ARCH in 'stack'.

This fixes the bug where we can't (currently) find the toolchain
for arm because it's at a different GCC version (4.8) from arm64 (4.9).

Change-Id: I22351af55298255f3ac4adfcae7e20080712fba4
1 file changed