devenv: add support for compiling to msvc targets with llvm/clang

devenv.nix

@@ -29,6 +29,8 @@ in
     pkg-config
     tree
     unzip
+    lld
+    xxd
   ];
 
   languages = {
@@ -47,11 +49,27 @@ in
     WINEPREFIX = "${config.env.DEVENV_ROOT}/wineprefix";
   };
 
-  enterShell = ''
-    wineboot
+  scripts = {
+    "clang-msvc".exec = ''
+      clang-cl -v -fuse-ld=lld -target x86_64-pc-windows-msvc \
+        -vctoolsdir $DEVENV_ROOT/xwin/crt -winsdkdir $DEVENV_ROOT/xwin/sdk \
+        "$@" \
+        /link /subsystem:console
+    '';
+  };
 
-    if [[ ! -e ./workspaces ]]; then
+  enterShell = ''
+    if [[ ! -e ${config.env.DEVENV_ROOT}/wineprefix ]]; then
+      wineboot
+    fi
+
+    if [[ ! -e ${config.env.DEVENV_ROOT}/workspaces ]]; then
       mkdir ./workspaces
     fi
+
+    if [[ ! -e ${config.env.DEVENV_ROOT}/xwin ]]; then
+      cargo install xwin
+      xwin --accept-license splat --preserve-ms-arch-notation --output ./xwin
+    fi
   '';
 }