gnu: Add gdc alias.

* gnu/packages/gcc.scm (gdc): New variable.

Change-Id: I38447e46ffba44d3a9d3757d34fe9ff081803457
Reviewed-by: Ludovic Courtès <ludo@gnu.org>

gnu/packages/gcc.scm

@@ -1124,6 +1124,12 @@ (define-public gdc-11
    (custom-gcc gcc-11 "gdc" '("d")
                %generic-search-paths)))
 
+;;; Alias tracking the latest GDC version.
+(define-public gdc
+  (hidden-package
+   (custom-gcc gcc "gdc" '("d")
+               %generic-search-paths)))
+
 (define-public (make-libgccjit gcc)
   (package
     (inherit gcc)