[K/N] Fix for KT-48807

Make NS_FORMAT_ARGUMENT(A) a no-op in cinterop because our
Clang doesn't support it for NSAttributedString.

kotlin-native/Interop/Indexer/src/main/kotlin/org/jetbrains/kotlin/native/interop/indexer/NativeIndex.kt

@@ -58,6 +58,34 @@ interface Compilation {
     val language: Language
 }
 
+fun defaultCompilerArgs(language: Language): List<String> =
+        listOf(
+                // We compile with -O2 because Clang may insert inline asm in bitcode at -O0.
+                // It is undesirable in case of watchos_arm64 since we target armv7k
+                // for this target instead of arm64_32 because it is not supported in LLVM 8.
+                //
+                // Note that PCH and the *.c file should be compiled with the same optimization level.
+                "-O2",
+                // Allow throwing exceptions through generated stubs.
+                "-fexceptions",
+        ) + when (language) {
+            Language.C -> emptyList()
+            Language.CPP -> emptyList()
+            Language.OBJECTIVE_C -> listOf(
+                    // "Objective-C" within interop means "Objective-C with ARC":
+                    "-fobjc-arc",
+                    // Using this flag here has two effects:
+                    // 1. The headers are parsed with ARC enabled, thus the API is visible correctly.
+                    // 2. The generated Objective-C stubs are compiled with ARC enabled, so reference counting
+                    // calls are inserted automatically.
+
+                    // Workaround for https://youtrack.jetbrains.com/issue/KT-48807.
+                    // TODO(LLVM): Remove after update to a version with
+                    //  https://github.com/apple/llvm-project/commit/2de0a18a8949f0235fb3a08dcc55ff3aa7d969e7.
+                    "-DNS_FORMAT_ARGUMENT(A)="
+            )
+        }
+
 data class CompilationWithPCH(
         override val compilerArgs: List<String>,
         override val language: Language

kotlin-native/Interop/Indexer/src/test/kotlin/org/jetbrains/kotlin/native/interop/indexer/WorkaroundTests.kt

@@ -26,11 +26,12 @@ class WorkaroundTests : IndexerTests() {
             
             NS_FORMAT_ARGUMENT(1) int f(const char* c);
         """.trimIndent()
+        val language = Language.OBJECTIVE_C
         val compilation = CompilationImpl(
                 includes = emptyList(),
                 additionalPreambleLines = code.split("\n"),
-                compilerArgs = listOf(),
-                language = Language.C
+                compilerArgs = defaultCompilerArgs(language),
+                language = language
         )
         withIndex { index ->
             val translationUnit = compilation.parse(

kotlin-native/Interop/StubGenerator/src/main/kotlin/org/jetbrains/kotlin/native/interop/gen/jvm/main.kt

@@ -477,34 +477,14 @@ internal fun buildNativeLibrary(
     val compilerOpts: List<String> = mutableListOf<String>().apply {
         addAll(def.config.compilerOpts)
         addAll(tool.getDefaultCompilerOptsForLanguage(language))
-        // We compile with -O2 because Clang may insert inline asm in bitcode at -O0.
-        // It is undesirable in case of watchos_arm64 since we target armv7k
-        // for this target instead of arm64_32 because it is not supported in LLVM 8.
-        //
-        // Note that PCH and the *.c file should be compiled with the same optimization level.
-        add("-O2")
-        // Allow throwing exceptions through generated stubs.
-        add("-fexceptions")
         addAll(additionalCompilerOpts)
         addAll(getCompilerFlagsForVfsOverlay(arguments.headerFilterPrefix.toTypedArray(), def))
-        addAll(when (language) {
-            Language.C -> emptyList()
-            Language.CPP -> emptyList()
-            Language.OBJECTIVE_C -> {
-                // "Objective-C" within interop means "Objective-C with ARC":
-                listOf("-fobjc-arc")
-                // Using this flag here has two effects:
-                // 1. The headers are parsed with ARC enabled, thus the API is visible correctly.
-                // 2. The generated Objective-C stubs are compiled with ARC enabled, so reference counting
-                // calls are inserted automatically.
-            }
-        })
     }
 
     val compilation = CompilationImpl(
             includes = headerFiles,
             additionalPreambleLines = def.defHeaderLines,
-            compilerArgs = compilerOpts + tool.platformCompilerOpts,
+            compilerArgs = defaultCompilerArgs(language) + compilerOpts + tool.platformCompilerOpts,
             language = language
     )