Export app certificates to Make for apkcerts list

Bug: 70669383
Test: m apkcerts-list contains framework-res.apk
Change-Id: I38af458e4262371c9c8368b5eebcff063a9bc359
diff --git a/android/config.go b/android/config.go
index bf8edca..56e9525 100644
--- a/android/config.go
+++ b/android/config.go
@@ -511,12 +511,13 @@
 	}
 }
 
-func (c *config) DefaultAppCertificate(ctx PathContext) SourcePath {
+func (c *config) DefaultAppCertificate(ctx PathContext) (pem, key SourcePath) {
 	defaultCert := String(c.ProductVariables.DefaultAppCertificate)
 	if defaultCert != "" {
-		return PathForSource(ctx, defaultCert)
+		return PathForSource(ctx, defaultCert+".x509.pem"), PathForSource(ctx, defaultCert+".pk8")
 	} else {
-		return c.DefaultAppCertificateDir(ctx).Join(ctx, "testkey")
+		defaultDir := c.DefaultAppCertificateDir(ctx)
+		return defaultDir.Join(ctx, "testkey.x509.pem"), defaultDir.Join(ctx, "testkey.pk8")
 	}
 }