Add aconfig flag support for android_library

This change adds the support that was added to android_app in
https://r.android.com/2854663 for android_library modules.

Implementation details:
- Move `Flags_packages` to aaptProperties, so that it can be utilized
  for both android_app and android_library.
- Wrap `VisitDirectDeps` of aconfig_declarations to a function that
  takes a ModuleContext as an input, so that it can be utilized in the
  `GenerateAndroidBuildActions` of both android_app and android_library.

Test: m nothing --no-skip-soong-tests
Bug: 330222981
Change-Id: I8a755f5ca615c8a1651afcd2ec441fc9fbd82c61

java/aar_test.go

@@ -81,3 +81,50 @@ func TestAarImportProducesJniPackages(t *testing.T) {
 		})
 	}
 }
+
+func TestLibraryFlagsPackages(t *testing.T) {
+	result := android.GroupFixturePreparers(
+		prepareForJavaTest,
+	).RunTestWithBp(t, `
+		android_library {
+			name: "foo",
+			srcs: ["a.java"],
+			sdk_version: "current",
+			flags_packages: [
+				"bar",
+				"baz",
+			],
+		}
+		aconfig_declarations {
+			name: "bar",
+			package: "com.example.package.bar",
+			srcs: [
+				"bar.aconfig",
+			],
+		}
+		aconfig_declarations {
+			name: "baz",
+			package: "com.example.package.baz",
+			srcs: [
+				"baz.aconfig",
+			],
+		}
+	`)
+
+	foo := result.ModuleForTests("foo", "android_common")
+
+	// android_library module depends on aconfig_declarations listed in flags_packages
+	android.AssertBoolEquals(t, "foo expected to depend on bar", true,
+		CheckModuleHasDependency(t, result.TestContext, "foo", "android_common", "bar"))
+
+	android.AssertBoolEquals(t, "foo expected to depend on baz", true,
+		CheckModuleHasDependency(t, result.TestContext, "foo", "android_common", "baz"))
+
+	aapt2LinkRule := foo.Rule("android/soong/java.aapt2Link")
+	linkInFlags := aapt2LinkRule.Args["inFlags"]
+	android.AssertStringDoesContain(t,
+		"aapt2 link command expected to pass feature flags arguments",
+		linkInFlags,
+		"--feature-flags @out/soong/.intermediates/bar/intermediate.txt --feature-flags @out/soong/.intermediates/baz/intermediate.txt",
+	)
+}