[vkloader][build] Convert GN libs lists to frameworks

Future versions of GN disallow naming frameworks in `libs` lists.
There's first-class support for `frameworks` instead, which is
preferred.  Switch to that.

Bug: 56683
Change-Id: I1300f0e3cbbabad9a63ff86fce717061381c249a
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/Vulkan-Loader/+/408794
Reviewed-by: Roland McGrath <mcgrathr@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index 4712f08..4b2022f 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -137,7 +137,7 @@
       libs = [ "Cfgmgr32.lib" ]
     }
     if (is_mac) {
-      libs = [ "CoreFoundation.framework" ]
+      frameworks = [ "CoreFoundation.framework" ]
     }
     if (build_with_chromium) {
       configs -= [ "//build/config/compiler:chromium_code" ]