These are only used for type checking, so don't bother importing them at
runtime.
Generally add future annotations at the same time, to make sure that
existing uses of these imports don't need to be quoted.
e7c972b606
added PACKAGE_VENDOR to lld, causing the -v output to start with "Homebrew LLD"
rather than just "LLD". Meson no longer detects it and fails the
test_ld_environment_variable_lld unit test.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>