Support patch_module in java modules

A few tests that have classes in the java.base module need to pass
--patch-module=java.base=<classpath> to javac.

Test: m checkbuild
Change-Id: I246bad92dcde976969b064aace5e2856e2bac971

java/builder.go

@@ -375,8 +375,11 @@ func TransformJarJar(ctx android.ModuleContext, outputFile android.WritablePath,
 type classpath []android.Path
 
 func (x *classpath) FormJavaClassPath(optName string) string {
+	if optName != "" && !strings.HasSuffix(optName, "=") && !strings.HasSuffix(optName, " ") {
+		optName += " "
+	}
 	if len(*x) > 0 {
-		return optName + " " + strings.Join(x.Strings(), ":")
+		return optName + strings.Join(x.Strings(), ":")
 	} else {
 		return ""
 	}