Move host flags from linux -> host

There will be a second linux host config (linux_bionic), so move this to
apply to all supported host configs instead of just linux_glibc.

Test: out/soong/build.ninja is the same before/after
Change-Id: Id8db10e0a3db889736070eea16f387785c913179
1 file changed
tree: ceb45db0fe50668746b23f4e49f76707b7d81d83
  1. libbacktrace/
  2. libunwindstack/