Allow cache_git.sh to handle additional projects adhoc

When testing external plugins it's extremely useful to be able to
cache additional repositories with cache_git.sh. This allows us to
just pass a whole set of additional items on the cli that will also
get cached.

Change-Id: I966c45efa9e8eb8868323de74f363eb1990e534e

cache_git.sh

@@ -57,6 +57,9 @@ while getopts hd: opt; do
     esac
 done
 
+for dir in $@; do
+    PROJECTS+="$dir "
+done
 
 function git_update_mirror {
     local project=$1