8001460: build-infra: Linker warnings on macosx
Summary: Only linking against jvm variant specific dirs if they are expected to exist.
Reviewed-by: ohair
8003300: build-infra: fails on solaris when objcopy is not found
Summary: Only call BASIC_FIXUP_EXECUTABLE() if objcopy was found.
Reviewed-by: tbell
Contributed-by: erik.joelsson@oracle.com