gotest: use a space rather than a middle dot in target lists

gotest: use a space rather than a middle dot in target lists

Replace the U+00B7 middle dot character, placed after "mips64p32le"
in the target lists, with a space.  The U+00B7 character may not be
considered whitespace by Bourne shell and any non-ASCII character
may render incorrectly in some terminal devices.

Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/251177