fix an uninitialized pointer in BridgedSourceLoc

It's so easy to run into undefined behavior in C++

SwiftCompilerSources/Sources/Basic/SourceLoc.swift

@@ -27,11 +27,11 @@ public struct SourceLoc {
     guard bridged.isValid() else {
       return nil
     }
-    self.locationInFile = bridged.opaquePointer!
+    self.locationInFile = bridged.uint8Pointer()!
   }
 
   public var bridged: BridgedSourceLoc {
-    .init(opaquePointer: locationInFile)
+    .init(locationInFile)
   }
 }