Move sysprop gen code to sysprop module

sysprop_library now generates srcjar itself, effectively cutting the
implicit dependency from java module to sysprop module.

Bug: 131637873
Test: m {sysprop_library}-dump-api
Test: m (with no arguments) performs API check
Change-Id: Ia11a744e74b6f733ff0e30d194fbba22505ed644

java/java.go

@@ -184,10 +184,6 @@ type CompilerProperties struct {
 		Output_params []string
 	}
 
-	Sysprop struct {
-		Platform *bool
-	} `blueprint:"mutated"`
-
 	Instrument bool `blueprint:"mutated"`
 
 	// List of files to include in the META-INF/services folder of the resulting jar.