PGI: Remove -A from the C++ flags we use when CXX_EXTENSIONS is OFF

Since commit 9b97cb5562 (PGI: Add language standards for PGI,
2017-05-01, v3.9.0-rc1~174^2), we have passed the `-A` flag to
the PGI C++ compiler when specifying a C++ standard flag with
compiler extensions turned off.  The flag is not meant for that.
The PGI C++ standard flags do not turn extensions on by default
and have a separate `--gnu_extensions` flag for that which we
already use when CXX_EXTENSIONS is ON.  Simply drop the `-A` flag.

Fixes: #20997

Modules/Compiler/PGI-CXX.cmake

@@ -4,19 +4,19 @@ string(APPEND CMAKE_CXX_FLAGS_MINSIZEREL_INIT " -DNDEBUG")
 string(APPEND CMAKE_CXX_FLAGS_RELEASE_INIT " -DNDEBUG")
 
 if(CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 12.10)
-  set(CMAKE_CXX98_STANDARD_COMPILE_OPTION  -A)
+  set(CMAKE_CXX98_STANDARD_COMPILE_OPTION "")
   set(CMAKE_CXX98_EXTENSION_COMPILE_OPTION --gnu_extensions)
   set(CMAKE_CXX98_STANDARD__HAS_FULL_SUPPORT ON)
   if(CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 13.10)
-    set(CMAKE_CXX11_STANDARD_COMPILE_OPTION  --c++11 -A)
+    set(CMAKE_CXX11_STANDARD_COMPILE_OPTION  --c++11)
     set(CMAKE_CXX11_EXTENSION_COMPILE_OPTION --c++11 --gnu_extensions)
     set(CMAKE_CXX11_STANDARD__HAS_FULL_SUPPORT ON)
     if(CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 15.7)
-      set(CMAKE_CXX14_STANDARD_COMPILE_OPTION  --c++14 -A)
+      set(CMAKE_CXX14_STANDARD_COMPILE_OPTION  --c++14)
       set(CMAKE_CXX14_EXTENSION_COMPILE_OPTION --c++14 --gnu_extensions)
       set(CMAKE_CXX14_STANDARD__HAS_FULL_SUPPORT ON)
       if(CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 17.1)
-        set(CMAKE_CXX17_STANDARD_COMPILE_OPTION  --c++17 -A)
+        set(CMAKE_CXX17_STANDARD_COMPILE_OPTION  --c++17)
         set(CMAKE_CXX17_EXTENSION_COMPILE_OPTION --c++17 --gnu_extensions)
         set(CMAKE_CXX17_STANDARD__HAS_FULL_SUPPORT ON)
       endif()