release-cross: remove alpha-elf target

This doesn’t appear to ever have worked. binutils doesn’t seem to
support the alpha-elf target at all. It doesn’t make sense to keep
this around.

https://hydra.nixos.org/build/92403855/nixlog/1/tail

lib/systems/examples.nix

@@ -131,11 +131,6 @@ rec {
     config = "powerpcle-none-eabi";
     libc = "newlib";
   };
-  
-  alpha-embedded = {
-    config = "alpha-elf";
-    libc = "newlib";
-  };
 
   i686-embedded = {
     config = "i686-elf";

pkgs/top-level/release-cross.nix

@@ -147,7 +147,6 @@ in
   aarch64-embedded = mapTestOnCross lib.systems.examples.aarch64-embedded embedded;
   i686-embedded = mapTestOnCross lib.systems.examples.i686-embedded embedded;
   x86_64-embedded = mapTestOnCross lib.systems.examples.x86_64-embedded embedded;
-  alpha-embedded = mapTestOnCross lib.systems.examples.alpha-embedded embedded;
 
   /* Cross-built bootstrap tools for every supported platform */
   bootstrapTools = let