Enable libdemangle and libunwindstack on host bionic

libunwindstack_test:UnwindTest.* are all failing, but at least this
builds.

Test: Enable host bionic; m
Test: out/soong/host/linux_bionic-x86/nativetest64/libdemangle_test/libdemangle_test
Test: out/soong/host/linux_bionic-x86/nativetest64/libunwindstack_test/libunwindstack_test
Change-Id: Ie6c774ecb4d7a467b5ea7ae977833e9cba178f2d