LLVM 18 std lib updates and fixes

* some manual fixes to generated CPU features code. In the future it
  would be nice to make the script do those automatically.

* add to various target OS switches. Some of the values I was unsure of
  and added TODO panics, for example in the case of spirv CPU arch.

src/Module.zig

@@ -5976,6 +5976,8 @@ pub fn atomicPtrAlignment(
         => 128,
 
         .x86_64 => if (std.Target.x86.featureSetHas(target.cpu.features, .cx16)) 128 else 64,
+
+        .spirv => @panic("TODO what should this value be?"),
     };
 
     const int_ty = switch (ty.zigTypeTag(mod)) {