Fortran: Detect pointer size on Intel archs with PGI (#14870)

The PGI compiler does not define __SIZEOF_POINTER__ so use the
__x86_64__ or __i386__ CPU macros to select a pointer size instead.

Modules/CMakeFortranCompilerABI.F

@@ -10,11 +10,15 @@
         PRINT *, 'INFO:sizeof_dptr[8]'
 #elif defined(_M_AMD64)
         PRINT *, 'INFO:sizeof_dptr[8]'
+#elif defined(__x86_64__)
+        PRINT *, 'INFO:sizeof_dptr[8]'
 
 #elif defined(_ILP32)
         PRINT *, 'INFO:sizeof_dptr[4]'
 #elif defined(_M_IX86)
         PRINT *, 'INFO:sizeof_dptr[4]'
+#elif defined(__i386__)
+        PRINT *, 'INFO:sizeof_dptr[4]'
 
 #elif defined(__SIZEOF_POINTER__) && __SIZEOF_POINTER__ == 8
         PRINT *, 'INFO:sizeof_dptr[8]'