Revert "Bump the DWARF version number to 5 on Darwin." (#95325)

Reverts #95164

This broke a buildbot:
https://lab.llvm.org/buildbot/#/builders/37/builds/35987

Author: fmayer

clang/lib/Driver/ToolChains/Darwin.cpp

@@ -1257,17 +1257,7 @@ unsigned DarwinClang::GetDefaultDwarfVersion() const {
   if ((isTargetMacOSBased() && isMacosxVersionLT(10, 11)) ||
       (isTargetIOSBased() && isIPhoneOSVersionLT(9)))
     return 2;
-  // Default to use DWARF 4 on OS X 10.11 - macOS 14 / iOS 9 - iOS 17.
-  if ((isTargetMacOSBased() && isMacosxVersionLT(15)) ||
-      (isTargetIOSBased() && isIPhoneOSVersionLT(18)) ||
-      (isTargetWatchOSBased() && TargetVersion < llvm::VersionTuple(11)) ||
-      (isTargetXROS() && TargetVersion < llvm::VersionTuple(2)) ||
-      (isTargetDriverKit() && TargetVersion < llvm::VersionTuple(24)) ||
-      (isTargetMacOSBased() &&
-       TargetVersion.empty()) || // apple-darwin, no version.
-      (TargetPlatform == llvm::Triple::BridgeOS))
-    return 4;
-  return 5;
+  return 4;
 }
 
 void MachO::AddLinkRuntimeLib(const ArgList &Args, ArgStringList &CmdArgs,

clang/test/Driver/debug-options.c

@@ -68,32 +68,7 @@
 // RUN: %clang -### -c -g %s -target x86_64-apple-driverkit19.0 2>&1 \
 // RUN:             | FileCheck -check-prefix=G_STANDALONE \
 // RUN:                         -check-prefix=G_DWARF4 %s
-// RUN: %clang -### -c -g %s -target x86_64-apple-macosx15 2>&1 \
-// RUN:             | FileCheck -check-prefix=G_STANDALONE \
-// RUN:                         -check-prefix=G_DWARF5 %s
-// RUN: %clang -### -c -g %s -target arm64-apple-ios17.0 2>&1 \
-// RUN:             | FileCheck -check-prefix=G_STANDALONE \
-// RUN:                         -check-prefix=G_DWARF4 %s
-// RUN: %clang -### -c -g %s -target arm64-apple-ios18.0 2>&1 \
-// RUN:             | FileCheck -check-prefix=G_STANDALONE \
-// RUN:                         -check-prefix=G_DWARF5 %s
-// RUN: %clang -### -c -g %s -target arm64_32-apple-watchos11 2>&1 \
-// RUN:             | FileCheck -check-prefix=G_STANDALONE \
-// RUN:                         -check-prefix=G_DWARF5 %s
-// RUN: %clang -### -c -g %s -target arm64-apple-tvos18.0 2>&1 \
-// RUN:             | FileCheck -check-prefix=G_STANDALONE \
-// RUN:                         -check-prefix=G_DWARF5 %s
-// RUN: %clang -### -c -g %s -target x86_64-apple-driverkit24.0 2>&1 \
-// RUN:             | FileCheck -check-prefix=G_STANDALONE \
-// RUN:                         -check-prefix=G_DWARF5 %s
-// RUN: %clang -### -c -g %s -target arm64-apple-xros1 2>&1 \
-// RUN:             | FileCheck -check-prefix=G_STANDALONE \
-// RUN:                         -check-prefix=G_DWARF4 %s
-// RUN: %clang -### -c -g %s -target arm64-apple-xros2 2>&1 \
-// RUN:             | FileCheck -check-prefix=G_STANDALONE \
-// RUN:                         -check-prefix=G_DWARF5 %s
-//
-// RUN: %clang -### -c -fsave-optimization-record %s    \
+// RUN: %clang -### -c -fsave-optimization-record %s \
 // RUN:        -target x86_64-apple-darwin 2>&1 \
 // RUN:             | FileCheck -check-prefix=GLTO_ONLY %s
 // RUN: %clang -### -c -g -fsave-optimization-record %s \