linux-user: Guard local FUTEX_CMD_MASK definition
Building linux-user on a host with Linux 7.2 kernel headers fails with a macro redefinition error for FUTEX_CMD_MASK. The kernel commit 3ca9595d9fb6 ("futex: Add support for unlocking robust futexes") expanded the mask to include the new FUTEX_ROBUST_UNLOCK and FUTEX_ROBUST_LIST32 flags, which conflicts with QEMU's local definition. Add a #ifndef guard so the host definition takes precedence when available. The local fallback is kept for older kernel headers (pre-2.6.29) that lack FUTEX_CMD_MASK or define a mask without FUTEX_CLOCK_REALTIME. Signed-off-by: Cédric Le Goater <clg@redhat.com> Reviewed-by: Pierrick Bouvier <pierrick.bouvier@oss.qualcomm.com> Reviewed-by: Philippe Mathieu-Daudé <philmd@oss.qualcomm.com> Signed-off-by: Helge Deller <deller@gmx.de>