pal: Remove usage of MAP_FILE

This flag is a compatibility flag and not required on most OSes.
Some, including Haiku, does not even define it.

Author: trungnt2910

src/coreclr/pal/src/map/map.cpp

@@ -108,11 +108,6 @@ MAPmmapAndRecord(
 #define MAP_ANON MAP_ANONYMOUS
 #endif
 
-/* Some platforms like Haiku does not provide MAP_FILE */
-#ifndef MAP_FILE
-#define MAP_FILE 0
-#endif
-
 void
 FileMappingCleanupRoutine(
     CPalThread *pThread,
@@ -2115,7 +2110,7 @@ void * MAPMapPEFile(HANDLE hFile, off_t offset)
 #endif
     SIZE_T reserveSize = 0;
     bool forceOveralign = false;
-    int readWriteFlags = MAP_FILE|MAP_PRIVATE|MAP_FIXED;
+    int readWriteFlags = MAP_PRIVATE|MAP_FIXED;
     int readOnlyFlags = readWriteFlags;
 
     ENTRY("MAPMapPEFile (hFile=%p offset=%zx)\n", hFile, offset);
@@ -2322,7 +2317,7 @@ void * MAPMapPEFile(HANDLE hFile, off_t offset)
         // If PAL_MAP_READONLY_PE_HUGE_PAGE_AS_SHARED is set to 1. map the readonly sections as shared
         // which works well with the behavior of the hugetlbfs
         if (mapAsShared != NULL && (strcmp(mapAsShared, "1") == 0))
-            readOnlyFlags = MAP_FILE|MAP_SHARED|MAP_FIXED;
+            readOnlyFlags = MAP_SHARED|MAP_FIXED;
     }
 
     //we have now reserved memory (potentially we got rebased).  Walk the PE sections and map each part