There's an issue with LLVM metadata support; it triggers an assert when trying to generate asm for code with metadata globals. This new pass is used as a workaround: it strips metadata from the module before it reaches the code generator. Obviously, this is disabled if LLVM doesn't support metadata.

[Environment] 
DFLAGS=-I@RUNTIME_DIR@ -I@RUNTIME_DIR@/lib/common -L-L%@P%/../lib -d-version=Tango -defaultlib=@RUNTIME_AIO@ -debuglib=@RUNTIME_AIO@