Introduce avf_build_flags_cc cc_defaults

These are similar to avf_build_rust_build flags, but for cc_* soong
modules.

In the immediate future this will be used for flag guarding
virtcpu-freq related changes to platform.dts.

This patch also adds avf_build_flags_cc as cc_defaults to all our
existing cc_* soong modules

Test: builds
Bug: 284369518
Change-Id: I19152675802548cd9efba30a40bccdbb14867fe1
diff --git a/vmbase/Android.bp b/vmbase/Android.bp
index e682773..07e1b4c 100644
--- a/vmbase/Android.bp
+++ b/vmbase/Android.bp
@@ -41,6 +41,7 @@
 // Used by extra cc_library_static linked into the final ELF.
 cc_defaults {
     name: "vmbase_cc_defaults",
+    defaults: ["avf_build_flags_cc"],
     nocrt: true,
     no_libcrt: true,
     system_shared_libs: [],