buildinfo_prop generates ro.build.version.known_codenames

The sysprop is now generated as the corresponding Make variable
PLATFORM_VERSION_KNOWN_CODENAMES is imported.

Bug: 236602028
Test: atest ComposHostTestCases
Change-Id: Ife7e87ce5de65b57c51d5565e288807cf8360b28
diff --git a/android/config.go b/android/config.go
index ef71292..cd902cb 100644
--- a/android/config.go
+++ b/android/config.go
@@ -793,6 +793,10 @@
 	return String(c.productVariables.Platform_version_last_stable)
 }
 
+func (c *config) PlatformVersionKnownCodenames() string {
+	return String(c.productVariables.Platform_version_known_codenames)
+}
+
 func (c *config) MinSupportedSdkVersion() ApiLevel {
 	return uncheckedFinalApiLevel(19)
 }