gn2bp: unconditionally remove -DANDROID for all host targets

It turns out, -DANDROID was not consistently applied across the chromium
code base, so it was removed for some targets where it shouldn't have
been.
Adding it to the host defaults solves this problem.

Test: //components/android/cronet:cronet
Change-Id: Ieff81727410c47a0d90d22b56348c6773f653a25
2 files changed