sstate: Fix EXTRA_STAGING_FIXMES handling

The code wasn't working properly, tweak so that it works as expected and
the grep expression includes the right patterns. Not sure this code has ever
worked prior to this.

(From OE-Core rev: 6a46a974611c5262efefc21a11adb736c0fb206a)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/sstate.bbclass

@@ -518,6 +518,7 @@ python sstate_hardcode_path () {
     for fixmevar in extra_staging_fixmes.split():
         fixme_path = d.getVar(fixmevar)
         sstate_sed_cmd += " -e 's:%s:FIXME_%s:g'" % (fixme_path, fixmevar)
+        sstate_grep_cmd += " -e '%s'" % (fixme_path)
 
     fixmefn =  sstate_builddir + "fixmepath"