Fixes for host bionic support

This enables linux_bionic for llvm-headers-no-generated-headers, which
was missing.

Then add some more ifdefs in the host-side config.h (that's used for
linux_bionic) to deal with differences between bionic and glibc/darwin's
libc.

Bug: 31559095
Test: Enable host bionic, run soong
Change-Id: Ie01d3317eb21edd861163722d40a354207fada66
2 files changed