build: disable restrict warning when using GCC 12.1-12.3

Prevents warning raised by a compiler bug when using GCC 12.1-12.3 with C++20

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105545

CHANGES.md

@@ -30,6 +30,7 @@ Changes from ns-3.40 to ns-3-dev
 
 * In preparation to enable C++20, the following actions have been taken due to compiler issues:
   * Precompiled headers have been disabled in GCC versions >= 12.2.
+  * The `restrict` warning has been disabled in GCC versions 12.1-12.3.1.
 
 ### Changed behavior
 

build-support/macros-and-definitions.cmake

@@ -251,6 +251,13 @@ if("${CMAKE_CXX_COMPILER_ID}" MATCHES "GNU")
         CACHE BOOL "Precompile module headers to speed up compilation" FORCE
     )
   endif()
+  if((CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL "12.1.0")
+          AND (CMAKE_CXX_COMPILER_VERSION VERSION_LESS "12.3.2")
+  )
+    # Disable warnings-as-errors for certain versions of GCC when C++20 is
+    # enabled https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105545
+    add_compile_options(-Wno-restrict)
+  endif()
   set(GCC TRUE)
   add_definitions(-fno-semantic-interposition)
   if(${NS3_COLORED_OUTPUT} OR "$ENV{CLICOLOR}")