[clang][Darwin] Error out when missing requested libarclite library

[keith]

Summary

Starting with the SDKs provided with Xcode 14.3, this library no longer
exists. Before this change this results in an opaque linker error in the
case that your deployment target is low enough that this library is
added. This produces a more useful error message in that case.

[keith]

Improve test

[fahadnayyar]

Adding 1 more test chage.

[fahadnayyar]

Rebasing to main.

[ravikandhadai]

clang/include/clang/Basic/DiagnosticDriverKinds.td

623

To be consistent with other error messages, it would better to rephrase as
"SDK does not contain 'libarclite' at the path '%0'; try increasing the minimum deployment target"

[keith]

Improve error message

[fahadnayyar]

LGTM

clang/include/clang/Basic/DiagnosticDriverKinds.td

 def warn_drv_moutline_atomics_unsupported_opt : Warning<
   "'%0' does not support '-%1'; flag ignored">,
   InGroup<OptionIgnored>;
 
 def warn_drv_darwin_sdk_invalid_settings : Warning<
   "SDK settings were ignored as 'SDKSettings.json' could not be parsed">,
   InGroup<DiagGroup<"darwin-sdk-settings">>;
 
+def err_drv_darwin_sdk_missing_arclite : Error<
+  "SDK does not contain 'libarclite' at the path '%0'; try increasing the minimum deployment target">;
+
 def err_drv_trivial_auto_var_init_stop_after_missing_dependency : Error<
   "'-ftrivial-auto-var-init-stop-after=*' is used without "
   "'-ftrivial-auto-var-init=zero' or '-ftrivial-auto-var-init=pattern'">;
 
 def err_drv_trivial_auto_var_init_stop_after_invalid_value : Error<
   "'-ftrivial-auto-var-init-stop-after=*' only accepts positive integers">;
 
 def warn_drv_msp430_hwmult_unsupported : Warning<

clang/lib/Driver/ToolChains/Darwin.cpp

void DarwinClang::AddLinkARCArgs(const ArgList &Args,
   else if (isTargetIOSSimulator())
     P += "iphonesimulator";
   else if (isTargetIPhoneOS())
     P += "iphoneos";
   else
     P += "macosx";
   P += ".a";
 
+  if (!getVFS().exists(P))
+    getDriver().Diag(clang::diag::err_drv_darwin_sdk_missing_arclite) << P;
+
   CmdArgs.push_back(Args.MakeArgString(P));
 }
 
 unsigned DarwinClang::GetDefaultDwarfVersion() const {
   // Default to use DWARF 2 on OS X 10.10 / iOS 8 and lower.
   if ((isTargetMacOSBased() && isMacosxVersionLT(10, 11)) ||
       (isTargetIOSBased() && isIPhoneOSVersionLT(9)))
     return 2;

clang/test/Driver/arclite-link-external-toolchain.c

 // RUN: rm -rf %t.tmpdir
 // RUN: mkdir -p %t.tmpdir/Xcode.app/Contents/Developers/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk
 // RUN: %clang -### -target x86_64-apple-macos10.10 -fobjc-link-runtime -lfoo \
 // RUN:   -isysroot %t.tmpdir/Xcode.app/Contents/Developers/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk \
 // RUN:   %s 2>&1 | FileCheck %s
 
+// CHECK: error: SDK does not contain 'libarclite' at the path '
+// CHECK: .tmpdir/Xcode.app/{{.*}}libarclite_macosx.a';
+// CHECK: try increasing the minimum deployment target
 // CHECK: -lfoo
 // CHECK: .tmpdir/Xcode.app/{{.*}}libarclite_macosx.a

clang/test/Driver/arclite-link.c

 // RUN: touch %t.o
-// RUN: %clang -### -target x86_64-apple-darwin10 -fobjc-link-runtime -lfoo -mmacosx-version-min=10.10 %t.o 2>&1 | FileCheck -check-prefix=CHECK-ARCLITE-OSX %s
+// RUN: mkdir -p %t.tmpdir/Xcode.app/Contents/Developers/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk
+// RUN: %clang -### -target x86_64-apple-darwin10 -fobjc-link-runtime -lfoo -mmacosx-version-min=10.10 %t.o \
+// RUN: -isysroot %t.tmpdir/Xcode.app/Contents/Developers/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk 2>&1 | FileCheck -check-prefix=CHECK-ARCLITE-OSX %s
 // RUN: %clang -### -target x86_64-apple-darwin10 -fobjc-link-runtime -mmacosx-version-min=10.11 %t.o 2>&1 | FileCheck -check-prefix=CHECK-NOARCLITE %s
 // RUN: %clang -### -target i386-apple-darwin10 -fobjc-link-runtime -mmacosx-version-min=10.7 %t.o 2>&1 | FileCheck -check-prefix=CHECK-NOARCLITE %s
 // RUN: %clang -### -target x86_64-apple-darwin10 -fobjc-link-runtime -nostdlib %t.o 2>&1 | FileCheck -check-prefix=CHECK-NOSTDLIB %s
 
+// CHECK-ARCLITE-OSX: .tmpdir/Xcode.app/{{.*}}libarclite_macosx.a';
+// CHECK-ARCLITE-OSX: try increasing the minimum deployment target
 // CHECK-ARCLITE-OSX: -lfoo
 // CHECK-ARCLITE-OSX: libarclite_macosx.a
 // CHECK-ARCLITE-OSX: -framework
 // CHECK-ARCLITE-OSX: Foundation
 // CHECK-ARCLITE-OSX: -lobjc
 // CHECK-NOARCLITE-NOT: libarclite
 // CHECK-NOSTDLIB-NOT: -lobjc