Revert "qtspeech: fix build on Darwin"

The ld64 issue has been fixed.

This reverts commit 23c83f33ec.

pkgs/development/libraries/qt-6/modules/qtspeech.nix

@@ -2,7 +2,6 @@
   qtModule,
   lib,
   stdenv,
-  llvmPackages,
   qtbase,
   qtmultimedia,
   pkg-config,
@@ -13,10 +12,7 @@
 
 qtModule {
   pname = "qtspeech";
-  nativeBuildInputs = [
-    pkg-config
-  ]
-  ++ lib.optionals stdenv.hostPlatform.isDarwin [ llvmPackages.lld ];
+  nativeBuildInputs = [ pkg-config ];
   buildInputs = lib.optionals stdenv.hostPlatform.isLinux [
     flite
     alsa-lib
@@ -26,9 +22,4 @@ qtModule {
     qtbase
     qtmultimedia
   ];
-  env = lib.optionalAttrs stdenv.hostPlatform.isDarwin {
-    # Work around ld64's libc++ hardening issue.
-    # TODO: Remove once #536365 reaches this branch.
-    NIX_CFLAGS_LINK = "-fuse-ld=lld";
-  };
 }