Rename the AVIF_ENABLE_WUNUSED_RESULT cmake option

Rename it AVIF_ENABLE_NODISCARD, which matches the corresponding C
macro's name.
diff --git a/.github/workflows/ci-unix-shared-installed.yml b/.github/workflows/ci-unix-shared-installed.yml
index 369e928..e065a7a 100644
--- a/.github/workflows/ci-unix-shared-installed.yml
+++ b/.github/workflows/ci-unix-shared-installed.yml
@@ -89,7 +89,7 @@
         -DAVIF_CODEC_AOM=SYSTEM
         -DAVIF_CODEC_AOM_DECODE=OFF -DAVIF_CODEC_AOM_ENCODE=ON
         -DAVIF_CODEC_DAV1D=SYSTEM
-        -DAVIF_ENABLE_WUNUSED_RESULT=ON -DAVIF_ENABLE_WERROR=ON
+        -DAVIF_ENABLE_NODISCARD=ON -DAVIF_ENABLE_WERROR=ON
         -DAVIF_BUILD_EXAMPLES=ON -DAVIF_BUILD_APPS=ON
         -DAVIF_BUILD_TESTS=ON -DAVIF_ENABLE_GTEST=ON -DAVIF_GTEST=LOCAL
         -DAVIF_BUILD_GDK_PIXBUF=ON  ${{ env.CMAKE_AVIF_FLAGS }}
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4883d97..f058442 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -46,7 +46,7 @@
 option(BUILD_SHARED_LIBS "Build shared avif library" ON)
 
 option(AVIF_ENABLE_WERROR "Treat all compiler warnings as errors" OFF)
-option(AVIF_ENABLE_WUNUSED_RESULT "Add [[nodiscard]] to some functions. CMake must be at least 3.21 to force C23" OFF)
+option(AVIF_ENABLE_NODISCARD "Add [[nodiscard]] to some functions. CMake must be at least 3.21 to force C23" OFF)
 
 option(AVIF_ENABLE_EXPERIMENTAL_YCGCO_R "Enable experimental YCgCo-R matrix code" OFF)
 option(AVIF_ENABLE_EXPERIMENTAL_GAIN_MAP
@@ -302,7 +302,7 @@
     endif()
 endif()
 
-if(AVIF_ENABLE_WUNUSED_RESULT)
+if(AVIF_ENABLE_NODISCARD)
     if(CMAKE_VERSION VERSION_GREATER_EQUAL 3.21.0)
         set(CMAKE_C_STANDARD 23)
         set_property(TARGET avif_obj PROPERTY C_STANDARD 23)