[flang][runtime] Fix INQUIRE(POS=n) for non-advancing I/O

Position inquiries need to account for offsets in records to be
accurate in the case of non-advancing I/O.

Differential Revision: https://reviews.llvm.org/D127789

flang/runtime/unit.h

@@ -96,7 +96,7 @@ public:
   void SetPosition(std::int64_t, IoErrorHandler &); // zero-based
   std::int64_t InquirePos() const {
     // 12.6.2.11 defines POS=1 as the beginning of file
-    return frameOffsetInFile_ + 1;
+    return frameOffsetInFile_ + recordOffsetInFrame_ + positionInRecord + 1;
   }
 
   ChildIo *GetChildIo() { return child_.get(); }