mmapForContinuousMode: Redo #95702: Align Linux's impl to __APPLE__'s a little.

I've made this small cosmetic changes,
`s/CountersOffsetInBiasMode/FileOffsetToCounters/`

Author: chapuni

compiler-rt/lib/profile/InstrProfilingFile.c

@@ -243,18 +243,20 @@ static int mmapForContinuousMode(uint64_t CurrentFileOffset, FILE *File) {
   if (getProfileFileSizeForMerging(File, &FileSize))
     return 1;
 
+  int Fileno = fileno(File);
+  uint64_t FileOffsetToCounters =
+      sizeof(__llvm_profile_header) + __llvm_write_binary_ids(NULL) + DataSize;
+
   /* Map the profile. */
   char *Profile = (char *)mmap(NULL, FileSize, PROT_READ | PROT_WRITE,
-                               MAP_SHARED, fileno(File), 0);
+                               MAP_SHARED, Fileno, 0);
   if (Profile == MAP_FAILED) {
     PROF_ERR("Unable to mmap profile: %s\n", strerror(errno));
     return 1;
   }
-  const uint64_t CountersOffsetInBiasMode =
-      sizeof(__llvm_profile_header) + __llvm_write_binary_ids(NULL) + DataSize;
   /* Update the profile fields based on the current mapping. */
   INSTR_PROF_PROFILE_COUNTER_BIAS_VAR =
-      (intptr_t)Profile - (uintptr_t)CountersBegin + CountersOffsetInBiasMode;
+      (intptr_t)Profile - (uintptr_t)CountersBegin + FileOffsetToCounters;
 
   /* Return the memory allocated for counters to OS. */
   lprofReleaseMemoryPagesToOS((uintptr_t)CountersBegin, (uintptr_t)CountersEnd);