Exclude files in .git from list of perl files

The .git directory might contain perl files, as hooks, for example.
Since we have no control over these they should be excluded from things
like our perlcritic checks.

Per offline report from Mike Blackwell.

src/tools/perlcheck/find_perl_files

@@ -11,5 +11,5 @@ find_perl_files () {
 		find . -type f -perm -100 -exec file {} \; -print |
 		egrep -i ':.*perl[0-9]*\>' |
 		cut -d: -f1
-	} | sort -u
+	} | sort -u | grep -v '^\./\.git/' 
 }