Always compile with isysroot on iOS to point to SDK root (#45436)

packages/flutter_tools/lib/src/base/build.dart

@@ -242,8 +242,16 @@ class AOTSnapshotter {
 
     const String embedBitcodeArg = '-fembed-bitcode';
     final String assemblyO = fs.path.join(outputPath, 'snapshot_assembly.o');
+    List<String> isysrootArgs;
+    if (isIOS) {
+      final String iPhoneSDKLocation = await xcode.iPhoneSdkLocation();
+      if (iPhoneSDKLocation != null) {
+        isysrootArgs = <String>['-isysroot', iPhoneSDKLocation];
+      }
+    }
     final RunResult compileResult = await xcode.cc(<String>[
       '-arch', targetArch,
+      if (isysrootArgs != null) ...isysrootArgs,
       if (bitcode) embedBitcodeArg,
       '-c',
       assemblyPath,
@@ -265,7 +273,7 @@ class AOTSnapshotter {
       '-Xlinker', '-rpath', '-Xlinker', '@loader_path/Frameworks',
       '-install_name', '@rpath/App.framework/App',
       if (bitcode) embedBitcodeArg,
-      if (bitcode && isIOS) ...<String>[embedBitcodeArg, '-isysroot', await xcode.iPhoneSdkLocation()],
+      if (isysrootArgs != null) ...isysrootArgs,
       '-o', appLib,
       assemblyO,
     ];

packages/flutter_tools/test/general.shard/base/build_test.dart

@@ -214,6 +214,7 @@ void main() {
 
   group('Snapshotter - AOT', () {
     const String kSnapshotDart = 'snapshot.dart';
+    const String kSDKPath = '/path/to/sdk';
     String skyEnginePath;
 
     _FakeGenSnapshot genSnapshot;
@@ -243,6 +244,8 @@ void main() {
       mockAndroidSdk = MockAndroidSdk();
       mockArtifacts = MockArtifacts();
       mockXcode = MockXcode();
+      when(mockXcode.iPhoneSdkLocation()).thenAnswer((_) => Future<String>.value(kSDKPath));
+
       bufferLogger = BufferLogger();
       for (BuildMode mode in BuildMode.values) {
         when(mockArtifacts.getArtifactPath(Artifact.snapshotDart,
@@ -334,8 +337,19 @@ void main() {
         'main.dill',
       ]);
 
-      verify(xcode.cc(argThat(contains('-fembed-bitcode')))).called(1);
-      verify(xcode.clang(argThat(contains('-fembed-bitcode')))).called(1);
+      final VerificationResult toVerifyCC = verify(xcode.cc(captureAny));
+      expect(toVerifyCC.callCount, 1);
+      final List<String> ccArgs = toVerifyCC.captured.first;
+      expect(ccArgs, contains('-fembed-bitcode'));
+      expect(ccArgs, contains('-isysroot'));
+      expect(ccArgs, contains(kSDKPath));
+
+      final VerificationResult toVerifyClang = verify(xcode.clang(captureAny));
+      expect(toVerifyClang.callCount, 1);
+      final List<String> clangArgs = toVerifyClang.captured.first;
+      expect(clangArgs, contains('-fembed-bitcode'));
+      expect(clangArgs, contains('-isysroot'));
+      expect(clangArgs, contains(kSDKPath));
 
       final File assemblyFile = fs.file(assembly);
       expect(assemblyFile.existsSync(), true);
@@ -380,8 +394,19 @@ void main() {
         'main.dill',
       ]);
 
-      verify(xcode.cc(argThat(contains('-fembed-bitcode')))).called(1);
-      verify(xcode.clang(argThat(contains('-fembed-bitcode')))).called(1);
+      final VerificationResult toVerifyCC = verify(xcode.cc(captureAny));
+      expect(toVerifyCC.callCount, 1);
+      final List<String> ccArgs = toVerifyCC.captured.first;
+      expect(ccArgs, contains('-fembed-bitcode'));
+      expect(ccArgs, contains('-isysroot'));
+      expect(ccArgs, contains(kSDKPath));
+
+      final VerificationResult toVerifyClang = verify(xcode.clang(captureAny));
+      expect(toVerifyClang.callCount, 1);
+      final List<String> clangArgs = toVerifyClang.captured.first;
+      expect(clangArgs, contains('-fembed-bitcode'));
+      expect(clangArgs, contains('-isysroot'));
+      expect(clangArgs, contains(kSDKPath));
 
       final File assemblyFile = fs.file(assembly);
       final File assemblyBitcodeFile = fs.file('$assembly.stripped.S');
@@ -431,6 +456,9 @@ void main() {
       verifyNever(xcode.cc(argThat(contains('-fembed-bitcode'))));
       verifyNever(xcode.clang(argThat(contains('-fembed-bitcode'))));
 
+      verify(xcode.cc(argThat(contains('-isysroot')))).called(1);
+      verify(xcode.clang(argThat(contains('-isysroot')))).called(1);
+
       final File assemblyFile = fs.file(assembly);
       expect(assemblyFile.existsSync(), true);
       expect(assemblyFile.readAsStringSync().contains('.section __DWARF'), true);