libcap: disable go for unsupported host platforms (#412336)

lib/systems/default.nix

@@ -556,7 +556,7 @@ let
                 "x86_64" = "amd64";
                 "wasm32" = "wasm";
               }
-              .${final.parsed.cpu.name} or (throw "Unknown CPU variant ${final.parsed.cpu.name} by Go");
+              .${final.parsed.cpu.name} or null;
             GOOS = if final.isWasi then "wasip1" else final.parsed.kernel.name;
 
             # See https://go.dev/wiki/GoArm

pkgs/by-name/li/libcap/package.nix

@@ -8,7 +8,8 @@
   usePam ? !isStatic,
   pam ? null,
   isStatic ? stdenv.hostPlatform.isStatic,
-  withGo ? pkgsBuildHost.go.meta.available,
+  go,
+  withGo ? lib.meta.availableOn stdenv.buildPlatform go && stdenv.hostPlatform.go.GOARCH != null,
 
   # passthru.tests
   bind,
@@ -47,7 +48,7 @@ stdenv.mkDerivation rec {
   ];
 
   nativeBuildInputs = lib.optionals withGo [
-    pkgsBuildHost.go
+    go
   ];
 
   buildInputs = lib.optional usePam pam;