Make installable arch-variant and static vs shared variant for cc modules

libc's native_bridge shared variant needs to be installable: false,
make the installable property arch-variant and allow the static and
shared clauses to override it.

This relands I8e0eaed2169e89520b07bb0326bb97ac0b4a70ac with fixes to
allow only the shared variant to be marked installable: false.

Bug: 204136549
Test: m checkbuild
Change-Id: Ie579b5ba56ca21f4d9243088afd5078d8c122a68