replace stub.c with b.addWriteFiles().add("empty.c", "") (#9)

build.zig

@@ -6,7 +6,7 @@ pub fn build(b: *std.Build) void {
 
     const lib = b.addStaticLibrary(.{
         .name = "vulkan-headers",
-        .root_source_file = .{ .path = "stub.c" },
+        .root_source_file = .{ .path = b.addWriteFiles().add("empty.c", "") },
         .target = target,
         .optimize = optimize,
     });

stub.c

@@ -1,2 +0,0 @@
-// This file exists for the Zig build sytem to work.
-// In order to "build" this library, there need to be some objects to link.