fixes following warning:
cc1plus: note: unrecognized command-line option '-Wno-c++20-attribute-extensions' ...

--- openal-soft-1.23.1/CMakeLists.txt.orig	2023-04-11 22:46:23.000000000 +0300
+++ openal-soft-1.23.1/CMakeLists.txt	2025-05-26 20:55:18.045962172 +0300
@@ -268,14 +268,9 @@
         -Wpedantic
         $<$<COMPILE_LANGUAGE:CXX>:-Wold-style-cast -Wnon-virtual-dtor -Woverloaded-virtual>)
 
-    check_cxx_compiler_flag(-Wno-c++20-attribute-extensions HAVE_WNO_CXX20_ATTR_EXT)
-    if(HAVE_WNO_CXX20_ATTR_EXT)
-        set(C_FLAGS ${C_FLAGS} $<$<COMPILE_LANGUAGE:CXX>:-Wno-c++20-attribute-extensions>)
-    else()
-        check_cxx_compiler_flag(-Wno-c++20-extensions HAVE_WNO_CXX20_EXT)
-        if(HAVE_WNO_CXX20_EXT)
-            set(C_FLAGS ${C_FLAGS} $<$<COMPILE_LANGUAGE:CXX>:-Wno-c++20-extensions>)
-        endif()
+    check_cxx_compiler_flag(-Wno-c++20-extensions HAVE_WNO_CXX20_EXT)
+    if(HAVE_WNO_CXX20_EXT)
+        set(C_FLAGS ${C_FLAGS} $<$<COMPILE_LANGUAGE:CXX>:-Wno-c++20-extensions>)
     endif()
 
     if(ALSOFT_WERROR)