Add test for LTO edge case

This test confirms the behavior when LTO is disabled generally but
then enabled for a specific target.

Bug: 261733821
Test: Unit test
Change-Id: I415cd0146f2b83d85654239550d129f87e9001bc

cc/lto_test.go

@@ -15,10 +15,11 @@
 package cc
 
 import (
-	"android/soong/android"
 	"strings"
 	"testing"
 
+	"android/soong/android"
+
 	"github.com/google/blueprint"
 )
 
@@ -177,3 +178,35 @@ func TestThinLtoOnlyOnStaticDep(t *testing.T) {
 		t.Errorf("'baz' expected to have flags %q, but got %q", w, libFooCFlags)
 	}
 }
+
+func TestLtoDisabledButEnabledForArch(t *testing.T) {
+	t.Parallel()
+	bp := `
+	cc_library {
+		name: "libfoo",
+		srcs: ["foo.c"],
+		host_supported:true,
+		lto: {
+			never: true,
+		},
+		target: {
+			android: {
+				lto: {
+					never: false,
+					thin: true,
+				},
+			},
+		},
+	}`
+	result := android.GroupFixturePreparers(
+		prepareForCcTest,
+	).RunTestWithBp(t, bp)
+
+	libFooWithLto := result.ModuleForTests("libfoo", "android_arm64_armv8-a_shared").Rule("ld")
+	libFooWithoutLto := result.ModuleForTests("libfoo", "linux_glibc_x86_64_shared").Rule("ld")
+
+	android.AssertStringDoesContain(t, "missing flag for LTO in variant that expects it",
+		libFooWithLto.Args["ldFlags"], "-flto=thin")
+	android.AssertStringDoesNotContain(t, "got flag for LTO in variant that doesn't expect it",
+		libFooWithoutLto.Args["ldFlags"], "-flto=thin")
+}