From https://codereview.chromium.org/2599243002/#msg24

This change broke cross-compile build for Chromium Linux.

Cross-compile failure for MIPS can be seen here:
http://www.rt-rk.com/mips-buildbot/builders/build_and_test_chromium_trunk_for_MIPS/builds/1445/steps/Build%20Chromium/logs/stdio

Same issue is present when cross-compiling for ARM Linux.

//build/nocompile.gni does not set --target option for Clang, which then
defaults to x86_64, but --sysroot is set according to target_cpu, and then Clang
tries to use appropriate sysroot (in MIPS case it is
//build/linux/debian_wheezy_mips-sysroot). This results in mismatch and missing
Clang internal include paths which lead to missing header files.