Fix generated headers of snapshot

For VNDK snapshot and SDK snapshot, deps files have been used to capture
generated headers. But exported deps might contain intermediate phony
files instead of actual header files, which are for optimization of
ninja. To correctly capture all headers, exported generated header files
are gathered separately.

Bug: 65377115
Test: m nothing
Change-Id: Ia03fa69186490a818578190e3c0bfb0261d1fd6e
diff --git a/cc/vndk.go b/cc/vndk.go
index f25861a..5aeb2e6 100644
--- a/cc/vndk.go
+++ b/cc/vndk.go
@@ -704,7 +704,7 @@
 		// We glob headers from include directories inside source tree. So we first gather
 		// all include directories inside our source tree. On the contrast, we manually
 		// collect generated headers from dependencies as they can't globbed.
-		generatedHeaders = append(generatedHeaders, l.exportedDeps()...)
+		generatedHeaders = append(generatedHeaders, l.exportedGeneratedHeaders()...)
 		for _, dir := range append(l.exportedDirs(), l.exportedSystemDirs()...) {
 			exportedIncludes[dir.String()] = true
 		}