abuild: unset option variables to prevent environment leaking in

In abuild's getopts loop, option variables such as "keep", "verbose",
etc are only set if the corresponding option is found. If such an option
is *not* found, any environment variable with the same name will leak
in, instead. Prevent this by explicitly unsetting almost all of them.

abuild.in

@@ -2865,7 +2865,7 @@ usage() {
 }
 
 APKBUILD="${APKBUILD:-./APKBUILD}"
-unset force
+unset color_opt force forceroot install_deps keep keep_build nodeps quiet verbose
 while getopts ":AcdD:fFhkKmnP:qrRs:uvV" opt; do
 	case $opt in
 		'A') echo "$CARCH"; exit 0;;