[Serialization] Suggest solution for SDK mods causing deserialization failures

Many deserialization failures at this points are caused by archives
installed over the SDK. Let's extend the current 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 any module named here was modified in the SDK, 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 any module named here was modified in the SDK, 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

test/Serialization/Recovery/crash-xref.swift

@@ -23,6 +23,8 @@
 
 // RUN: cat %t/normal_stderr | %FileCheck %s -check-prefixes=NORMALFAILURE
 // NORMALFAILURE-LABEL: *** DESERIALIZATION FAILURE ***
+// NORMALFAILURE-LABEL: *** If any module named here was modified in the SDK, please delete the ***
+// NORMALFAILURE-LABEL: *** swiftmodule files from the root and keep only swiftinterface files. ***
 // NORMALFAILURE-NEXT: module 'Client' with full misc version {{.*}}'
 // NORMALFAILURE-NEXT: Could not deserialize type for 'foo()'
 // NORMALFAILURE-NEXT: Caused by: top-level value not found
@@ -33,6 +35,8 @@
 
 // RUN: cat %t/error_stderr | %FileCheck %s -check-prefixes=ALLOWFAILURE
 // ALLOWFAILURE-LABEL: *** DESERIALIZATION FAILURE ***
+// ALLOWFAILURE-LABEL: *** If any module named here was modified in the SDK, please delete the ***
+// ALLOWFAILURE-LABEL: *** swiftmodule files from the root and keep only swiftinterface files. ***
 // ALLOWFAILURE-NEXT: module 'Client' with full misc version {{.*}}' (built with -experimental-allow-module-with-compiler-errors)
 // ALLOWFAILURE-NEXT: Could not deserialize type for 'foo()'
 // ALLOWFAILURE-NEXT: Caused by: top-level value not found