compiler: fix quoting of //go:linkname in error message
compiler: fix quoting of //go:linkname in error message

Change-Id: I2bb3fa67fac2b4fe32893cdad8f6e37261b11216
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/195718
Reviewed-by: Than McIntosh <4b2922593166fc595a9b1a408f34f5d3817fe9d2@google.com>
Reviewed-by: Cherry Zhang <d62e63aa42ce272d7b6a5055d97e942b33a34679@google.com>

golang/gofrontend,golang/gofrontend,golang/gofrontend,golang/gofrontend