Fix macOS test app build and update Xcode setup in workflow

Consolidate Xcode installation for macOS 15 and 26 to use the latest stable version. Additionally, fix a compilation error on macOS by adding a header guard and forward declaration for audit_token_t before including libproc.h.

Author: rikyoz

.github/workflows/test_macos.yml

@@ -86,7 +86,7 @@ jobs:
     - uses: actions/checkout@v6
 
     - name: Install XCode
-      if: ${{ contains(matrix.os, 'macos-15') }}
+      if: ${{ contains(matrix.os, 'macos-15') || contains(matrix.os, 'macos-26') }}
       uses: maxim-lobanov/setup-xcode@v1
       with:
         xcode-version: latest-stable
@@ -97,12 +97,6 @@ jobs:
       with:
         xcode-version: '15.3'
 
-    - name: Install XCode
-      if: ${{ contains(matrix.os, 'macos-26') }}
-      uses: maxim-lobanov/setup-xcode@v1
-      with:
-        xcode-version: '26.1'
-
     - name: Reinstall GCC 12 on macOS 14
       if: ${{ contains(matrix.os, 'macos-14') && contains(matrix.c_compiler, 'gcc-12') }}
       shell: bash

tests/src/utils/filesystem.hpp

@@ -18,6 +18,9 @@
 #include <windows.h>
 #elif defined( __APPLE__ )
 #include <array>
+// Workaround for building with latest macOS SDK
+#define _MACH_MESSAGE_H_ // NOLINT(*-reserved-identifier)
+struct audit_token_t;
 #include <libproc.h> // for proc_pidpath and PROC_PIDPATHINFO_MAXSIZE
 #include <unistd.h> // for getpid
 #elif defined( __FreeBSD__ ) || defined( __DragonFly__ )