Export cc vendor functions for usage by rust.

This CL exports and refactors some cc vendor-snapshot related functions
so they can be reused by rust modules to support vendor snapshotting.

Bug: 184042776
Test: m nothing
Change-Id: I12706e62ce0ac3b2b4298085fafc1d77b8e0a0c4
diff --git a/cc/snapshot_utils.go b/cc/snapshot_utils.go
index 8eb6164..7b62603 100644
--- a/cc/snapshot_utils.go
+++ b/cc/snapshot_utils.go
@@ -20,7 +20,7 @@
 )
 
 var (
-	headerExts = []string{".h", ".hh", ".hpp", ".hxx", ".h++", ".inl", ".inc", ".ipp", ".h.generic"}
+	HeaderExts = []string{".h", ".hh", ".hpp", ".hxx", ".h++", ".inl", ".inc", ".ipp", ".h.generic"}
 )
 
 func (m *Module) IsSnapshotLibrary() bool {
@@ -109,7 +109,7 @@
 		return ctx.Config().VndkSnapshotBuildArtifacts()
 	}
 
-	for _, image := range []snapshotImage{vendorSnapshotImageSingleton, recoverySnapshotImageSingleton} {
+	for _, image := range []snapshotImage{VendorSnapshotImageSingleton, recoverySnapshotImageSingleton} {
 		if isSnapshotAware(ctx.DeviceConfig(), m, image.isProprietaryPath(ctx.ModuleDir(), ctx.DeviceConfig()), apexInfo, image) {
 			return true
 		}