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/xbps-src/shutils/show.sh

@@ -12,7 +12,9 @@ show_pkg() {
     for i in ${checksum}; do
         [ -n "$i" ] && echo "checksum:	$i"
     done
-    [ -n "$noarch" ] && echo "noarch:		yes"
+    for i in ${archs}; do
+        [ -n "$i" ] && echo "archs:		$i"
+    done
     echo "maintainer:	$maintainer"
     [ -n "$homepage" ] && echo "Upstream URL:	$homepage"
     [ -n "$license" ] && echo "License(s):	$license"