nix: add option to disable simd in libghostty-vt package

.github/workflows/test.yml

@@ -770,12 +770,24 @@ jobs:
       - name: Check to see if the library looks sane
         run: nm result/lib/libghostty-vt.so.0.1.0 2>&1 | grep -q 'ghostty_terminal_new'
 
+      - name: Test ReleaseFast (no SIMD) build of libghostty-vt
+        run: nix build .#libghostty-vt-releasefast-no-simd
+
+      - name: Check to see if the library looks sane
+        run: nm result/lib/libghostty-vt.so.0.1.0 2>&1 | grep -q 'ghostty_terminal_new'
+
       - name: Test Debug build of libghostty-vt
         run: nix build .#libghostty-vt-debug
 
       - name: Check to see if the library looks sane
         run: nm result/lib/libghostty-vt.so.0.1.0 2>&1 | grep -q 'ghostty_terminal_new'
 
+      - name: Test Debug (no SIMD) build of libghostty-vt
+        run: nix build .#libghostty-vt-debug-no-simd
+
+      - name: Check to see if the library looks sane
+        run: nm result/lib/libghostty-vt.so.0.1.0 2>&1 | grep -q 'ghostty_terminal_new'
+
   build-dist:
     runs-on: namespace-profile-ghostty-sm
     needs: test

flake.nix

@@ -106,6 +106,9 @@
         libghostty-vt-debug = pkgs.callPackage ./nix/libghostty-vt.nix (mkPkgArgs "Debug");
         libghostty-vt-releasesafe = pkgs.callPackage ./nix/libghostty-vt.nix (mkPkgArgs "ReleaseSafe");
         libghostty-vt-releasefast = pkgs.callPackage ./nix/libghostty-vt.nix (mkPkgArgs "ReleaseFast");
+        libghostty-vt-debug-no-simd = pkgs.callPackage ./nix/libghostty-vt.nix ((mkPkgArgs "Debug") // {simd = false;});
+        libghostty-vt-releasesafe-no-simd = pkgs.callPackage ./nix/libghostty-vt.nix ((mkPkgArgs "ReleaseSafe") // {simd = false;});
+        libghostty-vt-releasefast-no-simd = pkgs.callPackage ./nix/libghostty-vt.nix ((mkPkgArgs "ReleaseFast") // {simd = false;});
 
         libghostty-vt = libghostty-vt-releasefast;
       });

nix/libghostty-vt.nix

@@ -7,6 +7,7 @@
   zig_0_15,
   revision ? "dirty",
   optimize ? "Debug",
+  simd ? true,
 }:
 stdenv.mkDerivation (finalAttrs: {
   pname = "ghostty";
@@ -55,6 +56,7 @@ stdenv.mkDerivation (finalAttrs: {
     "-Doptimize=${optimize}"
     "-Dapp-runtime=none"
     "-Demit-lib-vt=true"
+    "-Dsimd=${lib.boolToString simd}"
   ];
 
   outputs = [