ModuleInterface: sanitize arch when interface file name and encoded flags disagree

It's a known issue that we are using arm64e interfaces contents for the arm64 target,
meaning the encoded module flags are specifying -target arm64e-x-x instead of
-target arm64-x-x. Fortunately, we can tell the target arch from the interface file
name, so we could sanitize the target to use by inferring arch from the file name.

include/swift/Serialization/SerializedModuleLoader.h

@@ -469,7 +469,8 @@ public:
 };
 
 /// Extract compiler arguments from an interface file buffer.
-bool extractCompilerFlagsFromInterface(StringRef buffer, llvm::StringSaver &ArgSaver,
+bool extractCompilerFlagsFromInterface(StringRef interfacePath,
+                                       StringRef buffer, llvm::StringSaver &ArgSaver,
                                        SmallVectorImpl<const char *> &SubArgs);
 
 /// Extract the user module version number from an interface file.