Added java_system_modules_import

A prebuilt version of java_system_modules. It does not import the
generated system module, it generates the system module from imported
java libraries in the same way that java_system_modules does. It just
acts as a prebuilt, i.e. can have the same base name as another module
type and the one to use is selected at runtime.

Bug: 142940300
Test: m nothing
Change-Id: I126db49d18294fcd6e2b7ad0237f83e9c2fdef7a
diff --git a/java/java_test.go b/java/java_test.go
index 5791619..a2788cb 100644
--- a/java/java_test.go
+++ b/java/java_test.go
@@ -1261,3 +1261,33 @@
 		}
 	}
 }
+
+func TestJavaSystemModulesImport(t *testing.T) {
+	ctx, _ := testJava(t, `
+		java_system_modules_import {
+			name: "system-modules",
+			libs: ["system-module1", "system-module2"],
+		}
+		java_import {
+			name: "system-module1",
+			jars: ["a.jar"],
+		}
+		java_import {
+			name: "system-module2",
+			jars: ["b.jar"],
+		}
+		`)
+
+	// check the existence of the module
+	systemModules := ctx.ModuleForTests("system-modules", "android_common")
+
+	cmd := systemModules.Rule("jarsTosystemModules")
+
+	// make sure the command compiles against the supplied modules.
+	for _, module := range []string{"system-module1.jar", "system-module2.jar"} {
+		if !strings.Contains(cmd.Args["classpath"], module) {
+			t.Errorf("system modules classpath %v does not contain %q", cmd.Args["classpath"],
+				module)
+		}
+	}
+}