Also do 32-bit GN builds on 64-bit Windows bots
Also do 32-bit GN builds on 64-bit Windows bots

NaCl's 32-bit Windows bots cannot do GN builds at all because the
Windows toolchains used by GN do not support 32-bit hosts.  To get at
least compile-testing of the GN builds for 32-bit Windows, also build
the 32-bit version on 64-bit Windows bots (though it cannot be tested).

BUG= none
TEST= trybots
R=bradnelson@chromium.org

Review URL: https://codereview.chromium.org/1802373004

sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client