Add debug ramdisk variant

A module will be installed to debug_ramdisk (or
debug_ramdisk/first_stage_ramdisk if recovery as boot is true) if
debug_ramdisk is set to true.

Bug: 184004542
Test: soong test
Change-Id: Ic5a4d27407e506fffa462de2149e0785f11b2ac7

rust/image.go

@@ -35,6 +35,10 @@ func (mod *Module) RamdiskVariantNeeded(android.BaseModuleContext) bool {
 	return mod.InRamdisk()
 }
 
+func (mod *Module) DebugRamdiskVariantNeeded(ctx android.BaseModuleContext) bool {
+	return false
+}
+
 func (mod *Module) RecoveryVariantNeeded(android.BaseModuleContext) bool {
 	return mod.InRecovery()
 }