os: unexport xthread_sigmask

This function isn't used by drivers and there's currently no need to do so,
thus keep it out of the public module API.

Fixes: 30ac756798
Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1368>

hw/xfree86/os-support/shared/sigio.c

@@ -59,6 +59,8 @@
 #include <errno.h>
 #include <X11/X.h>
 
+#include "os/osdep.h"
+
 #include <xserver_poll.h>
 #include "xf86.h"
 #include "xf86Priv.h"

include/os.h

@@ -510,7 +510,4 @@ xorg_backtrace(void);
 typedef _sigset_t sigset_t;
 #endif
 
-extern _X_EXPORT int
-xthread_sigmask(int how, const sigset_t *set, sigset_t *oldest);
-
 #endif                          /* OS_H */

os/osdep.h

@@ -166,4 +166,8 @@ void AutoResetServer(int sig);
 /* clone fd so it gets out of our select mask */
 int os_move_fd(int fd);
 
+/* set signal mask - either on current thread or whole process,
+   depending on whether multithreading is used */
+int xthread_sigmask(int how, const sigset_t *set, sigset_t *oldest);
+
 #endif                          /* _OSDEP_H_ */