Update Nix derivation to build against 22.05 and LLVM 11 (#601)

Also enable AArch64.

.github/workflows/main.yml

@@ -366,7 +366,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        nixpkgs: ['unstable', '21.05']
+        nixpkgs: ['unstable', '22.05']
         cuda: ['false', 'true']
     steps:
       - uses: actions/[email protected]

default.nix

@@ -5,7 +5,7 @@
 
 let
 
-  llvmPackages = pkgs.llvmPackages_10;
+  llvmPackages = pkgs.llvmPackages_11;
   stdenv = llvmPackages.stdenv;
   cuda = if cudaPackages ? cudatoolkit_11 then [
            cudaPackages.cudatoolkit_11
@@ -91,7 +91,7 @@ in stdenv.mkDerivation rec {
   meta = with lib; {
     description = "A low-level counterpart to Lua";
     homepage = "http://terralang.org/";
-    platforms = platforms.x86_64;
+    platforms = platforms.x86_64 ++ platforms.aarch64;
     maintainers = with maintainers; [ jb55 thoughtpolice ];
     license = licenses.mit;
   };