This behaves slightly differently than it does in the make based build.
1. The make based build manually passes -DGTEST_OS_ANDROID (or
whatever). gtest-port.h already has logic that does this, so it's a
no-op.
2. Host libraries are named identically, rather than libgtest_host.
Change-Id: Ic40a1025c698611d202cb7c8ec45abd8fe130065