Add native aarch64-linux builds

Previously, we were cross building for aarch64-linux, but
now we're running into the following problem:

    qemu: uncaught target signal 11 (Segmentation fault) - core dumped
    iserv-proxy: {handle: <socket: 5>}: GHCi.Message.remoteCall: end of file

    <no location info>: error: ghc-iserv terminated (1)

Now that we have an aarch64-linux runner, we'll just use that and we
don't have to deal with cross builds and TH.

Author: sgillespie

flake.nix

@@ -32,6 +32,7 @@
         "x86_64-linux"
         "x86_64-darwin"
         "aarch64-darwin"
+        "aarch64-linux"
       ];
     in
       inputs.utils.lib.eachSystem supportedSystems (system:
@@ -176,10 +177,7 @@
             '';
 
             crossPlatforms = p:
-              lib.optional (system == "x86_64-linux") p.musl64 ++
-              lib.optional
-                (system == "x86_64-linux" && config.compiler-nix-name == "ghc967")
-                p.aarch64-multiplatform-musl;
+              lib.optional (system == "x86_64-linux") p.musl64;
 
             inputMap = {
               "https://chap.intersectmbo.org/" = inputs.CHaP;