Add host_linux target properties

Add host_linux to the target properties, which will apply to linux_glibc,
linux_bionic or linux_musl.  This will eventually undo the hack that
makes the linux_glibc properties apply to linux_musl.

Bug: 223257095
Test: TestArchProperties
Change-Id: Iccf51ed13c363ce1da04333a277fa49c33d45b9a