common: merge only_for_archs and noarch=yes into one.

* noarch=yes is replaced with archs=noarch
* only_for_archs= is renamed to archs=
* archs= allows the use of wildcards and negations; first matching rule applies:
  * archs="*-musl" will build the pkg only for musl-libcs
  * archs="~*-musl" will build the pkg only on non-musl-libc
  * archs="x86_64-musl ~*-musl" will build for x86_64-musl and any non-musl
    arch.
* archs= defaults to "*"

common/hooks/post-install/06-strip-and-debug-pkgs.sh

@@ -59,7 +59,7 @@ create_debug_pkg() {
 hook() {
 	local fname= x= f= _soname= STRIPCMD=
 
-	if [ -n "$nostrip" -o -n "$noarch" ]; then
+	if [ -n "$nostrip" -o "${archs// /}" = "noarch" ]; then
 		return 0
 	fi