fix(build): fix repo detection for special chars in package name

Currently we used grep -E, in a way that special characters in the
package name such as the '+' in 'ls++' also became part of the regex.

This commit switches this to become a literal string matching using awk.

Signed-off-by: Christian Heusel <christian@heusel.eu>

src/lib/util/pacman.sh

@@ -44,7 +44,7 @@ get_pacman_repo_from_pkgbuild() {
 		-S \
 		--print \
 		--print-format '%n %r' \
-		"${pkgnames[0]}" | grep -E "^${pkgnames[0]} " | awk '{print $2}'
+		"${pkgnames[0]}" | awk '$1=="'"${pkgnames[0]}"'"{print $2}'
 	)
 	lock_close 10