xbps-src: new target: show-avail and returns 0 if pkg can be built.

common/xbps-src/shutils/show.sh

@@ -47,10 +47,13 @@ show_pkg_files() {
     [ -d ${PKGDESTDIR} ] && find ${PKGDESTDIR} -print
 }
 
+show_avail() {
+    check_pkg_arch "$XBPS_CROSS_BUILD" 2>/dev/null
+}
+
 show_pkg_build_deps() {
     local f x _pkgname _dep found result
 
-    check_pkg_arch "$XBPS_CROSS_BUILD"
     setup_pkg_depends
 
     result=$(mktemp || exit 1)

xbps-src

@@ -61,6 +61,10 @@ remove-autodeps
 show <pkgname>
     Show information for the specified package.
 
+show-avail <pkgname>
+    Returns 0 if package can be built for the given architecture,
+    any other error otherwise.
+
 show-build-deps <pkgname>
     Show required build dependencies for <pkgname>.
 
@@ -637,6 +641,10 @@ case "$XBPS_TARGET" in
         read_pkg
         show_pkg
         ;;
+    show-avail)
+        read_pkg
+        show_avail
+        ;;
     show-files)
         read_pkg
         show_pkg_files