Cherrypick "android: Support host multilib builds."

Take not-yet-landed upstream patch from
https://codereview.chromium.org/301373002/ to unblock host multilib
work.

> The Android build system now supports multilib 32/64-bit host builds as
> well as target builds, and Chromium needs to make use of this to
> properly support compiling V8 for host. Introduce a GYP_HOST_VAR_PREFIX
> variable that works equivalently to GYP_VAR_PREFIX and use it in all the
> places where the first/second host architecture must be selected, and
> also introduce GYP_HOST_MULTILIB to enable the top level makefile to
> specify whether it wants 32-bit or 64-bit host binaries.
>
> BUG=chromium:358141

Bug: 14826931
Change-Id: I7d55bc4c1b27acddd7ff192f8d3a6cb7ff724c9e
1 file changed