The linker uses libc++_static but needs to avoid the libc.a
dependency. It does this by setting `stl: "none"` and manually
linking libc++. This behavior matches make.
A better approach would probably be to generalize system_shared_libs
to system_libs and apply those to static executables the same way we
do for dynamic ones, but that's a patch for another day.
Test: make checkbuild
Bug: http://b/34740564
Change-Id: Ie9da0d49a453a220593e8ec2ee721e9af9378007
dc2597d25a