Fix bashisms in Make.coverity
Fix bashisms in Make.coverity

Not everybody uses bash as /bin/sh, and the scripting here is safe
just using single brackets.

Signed-off-by: Steve McIntyre <4b9a82601e055a676600cb7bb2498a6443c87488@debian.org>

rhinstaller/shim,rhinstaller/shim,rhinstaller/shim