cc: Make export_include_dirs configurable

Bug: 325444956
Test: m
Test: m [custom cc_library_headers with select]
Change-Id: Iebd66bb3f322276ff0f16dc7765257ea309b081f
diff --git a/cc/cmake_snapshot.go b/cc/cmake_snapshot.go
index c21a46f..5712d5e 100644
--- a/cc/cmake_snapshot.go
+++ b/cc/cmake_snapshot.go
@@ -507,7 +507,7 @@
 	moduleDir := ctx.OtherModuleDir(m) + string(filepath.Separator)
 	switch decorator := m.compiler.(type) {
 	case *libraryDecorator:
-		return sliceWithPrefix(moduleDir, decorator.flagExporter.Properties.Export_include_dirs)
+		return sliceWithPrefix(moduleDir, decorator.flagExporter.Properties.Export_include_dirs.GetOrDefault(ctx, nil))
 	}
 	return nil
 }