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

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.

Differential Revision: https://reviews.llvm.org/D150988

Author: keith

clang/include/clang/Basic/DiagnosticDriverKinds.td

@@ -619,6 +619,9 @@ 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'">;

clang/lib/Driver/ToolChains/Darwin.cpp

@@ -1221,6 +1221,9 @@ void DarwinClang::AddLinkARCArgs(const ArgList &Args,
     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));
 }
 

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

@@ -4,5 +4,8 @@
 // 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

@@ -1,9 +1,13 @@
 // 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