[Serialization] Suggest a fix for roots in deserialization failures

Most deserialization failures at this points are caused by roots
installed over the SDK. Let's extend the error message with a solution
for such a case.

rdar://86280699

Author: xymus

lib/Serialization/ModuleFileSharedCore.cpp

@@ -564,6 +564,8 @@ void ModuleFileSharedCore::fatal(llvm::Error error) const {
   llvm::raw_svector_ostream out(errorStr);
 
   out << "*** DESERIALIZATION FAILURE ***\n";
+  out << "*** If an SDK root installed any module named below, please delete the  ***\n";
+  out << "*** swiftmodule files from the root and keep only swiftinterface files. ***\n";
   outputDiagnosticInfo(out);
   out << "\n";
   if (error) {

test/Serialization/Recovery/crash-recovery.swift

@@ -17,5 +17,7 @@ public class Sub: Base {
 // CHECK-CRASH-4_2: Compiling with effective version 4.2
 // CHECK-CRASH: While loading members for 'Sub' (in module 'Lib')
 // CHECK-CRASH-LABEL: *** DESERIALIZATION FAILURE ***
+// CHECK-CRASH-LABEL: *** If an SDK root installed any module named below, please delete the  ***
+// CHECK-CRASH-LABEL: *** swiftmodule files from the root and keep only swiftinterface files. ***
 // CHECK-CRASH: module 'Lib' with full misc version {{.*}}4.1.50
 // CHECK-CRASH: could not find 'disappearingMethod()' in parent class