Add ld.gold and ld.lld compiler wrapper (#25626)

The gcc compiler can be configured to use `ld.gold` by default. It will
then call `ld.gold` explicitly when linking. When so, spack need to have
a ld.gold wrapper in PATH to inject rpaths link flags etc...

Also I wouldn't be surprised to see some package calling `ld.gold`
directly.

As for ld.gold, the argument could be made that we want to support any
package that could call ld.lld.

lib/spack/env/cc

@@ -163,7 +163,7 @@ case "$command" in
         lang_flags=F
         debug_flags="-g"
         ;;
-    ld)
+    ld|ld.gold|ld.lld)
         mode=ld
         ;;
     *)

lib/spack/env/ld.gold

@@ -0,0 +1 @@
+cc

lib/spack/env/ld.lld

@@ -0,0 +1 @@
+cc