Use default app certificate from Make

Bug: 69917341
Test: m checkbuild
Test: framework-res.apk is identical after converting to Soong
Change-Id: I6980afd94ea130740da0defeea045eddc2fc6439
diff --git a/android/config.go b/android/config.go
index 2589f71..8ae6471 100644
--- a/android/config.go
+++ b/android/config.go
@@ -491,11 +491,21 @@
 }
 
 func (c *config) DefaultAppCertificateDir(ctx PathContext) SourcePath {
-	return PathForSource(ctx, "build/target/product/security")
+	defaultCert := String(c.ProductVariables.DefaultAppCertificate)
+	if defaultCert != "" {
+		return PathForSource(ctx, filepath.Dir(defaultCert))
+	} else {
+		return PathForSource(ctx, "build/target/product/security")
+	}
 }
 
 func (c *config) DefaultAppCertificate(ctx PathContext) SourcePath {
-	return c.DefaultAppCertificateDir(ctx).Join(ctx, "testkey")
+	defaultCert := String(c.ProductVariables.DefaultAppCertificate)
+	if defaultCert != "" {
+		return PathForSource(ctx, defaultCert)
+	} else {
+		return c.DefaultAppCertificateDir(ctx).Join(ctx, "testkey")
+	}
 }
 
 func (c *config) AllowMissingDependencies() bool {