What steps will reproduce the problem?

set GYP_DEFINES=target_arch=ia32 libyuv_enable_svn=1
set DEPOT_TOOLS_WIN_TOOLCHAIN=0
call python gyp_libyuv -fninja -G msvs_version=2013 libyuv_test.gyp

What is the expected output? 
gyp_libyuv should be fast

What do you see instead?
gyp_libyuv takes about 30 seconds.

Please use labels and text to provide additional information.
A build without DEPOT_TOOLS_WIN_TOOLCHAIN is fast

set DEPOT_TOOLS_WIN_TOOLCHAIN=0 is required for compilers other than vs2013.

set GYP_DEFINES=target_arch=ia32 libyuv_enable_svn=1
call python gyp_libyuv -fninja -G msvs_version=2013 libyuv_test.gyp