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
237673d052