These files are used to select s390x assembler support in the gc
    toolchain.  We don't currently have that support, as it is written in
    the cmd/asm syntax rather than gas syntax.  Mark the files to be ignored
    for now, falling back to the default implementations.
    
    Patch by Andreas Krebbel.
    
    Reviewed-on: https://go-review.googlesource.com/26994

From-SVN: r239442