libmakepkg: fix compatibility with bash-5.2 patsub_replacement
Bash-5.2 introduced the patsub_replacement shell option, which is enabled by default. Apparently is it supposed to handle a sed-like idiom, but what it does achieve is making any substitution involving a "&" requiring special care.
For makepkg's DLAGENTS, we replace "%o" and "%u" if present. Any "&" in the replacement fields triggers patsub_replacement unless quoted. This is particularly important for the URL field.
Add relevant quotes to avoid issues.
Signed-off-by: Allan McRae allan@archlinux.org