[Serialization] Only remark if the last digit mismatches in precise tag check

Weaken the precise tag check at loading swiftmodule to accept binary
modules build by a compiler with a tag where only the last digit is
different. We assume that the other digit in the version should ensure
compiler and stdlib compatibility. If the last digit doesn't match,
still raise a remark.

rdar://105158258

lib/Serialization/SerializedModuleLoader.cpp

@@ -836,6 +836,13 @@ LoadedFile *SerializedModuleLoaderBase::loadAST(
     if (loadedModuleFile &&
         loadedModuleFile->mayHaveDiagnosticsPointingAtBuffer())
       OrphanedModuleFiles.push_back(std::move(loadedModuleFile));
+  } else {
+    // Report non-fatal compiler tag mismatch.
+    if (!loadInfo.problematicRevision.empty()) {
+      Ctx.Diags.diagnose(*diagLoc,
+                         diag::serialization_module_problematic_revision,
+                         loadInfo.problematicRevision, moduleBufferID);
+    }
   }
 
   // The -experimental-hermetic-seal-at-link flag turns on dead-stripping
@@ -896,7 +903,7 @@ void swift::serialization::diagnoseSerializedASTLoadFailure(
     break;
   case serialization::Status::RevisionIncompatible:
     Ctx.Diags.diagnose(diagLoc, diag::serialization_module_incompatible_revision,
-                       ModuleName, moduleBufferID);
+                       loadInfo.problematicRevision, ModuleName, moduleBufferID);
     break;
   case serialization::Status::Malformed:
     Ctx.Diags.diagnose(diagLoc, diag::serialization_malformed_module,