sched.h: Hide all Linux compat sched_* functions under _WITH_CPU_SET_T

Instead of only hiding cpu_set_t compat typedef itself.

Too many software packages assume that sched_getaffinity() presence
implies full source compatibility with glibc.  We can (and should)
handle missing CPU_* macros, but then there are incompatible BIT_* uses
which cannot be fixed in src/.

So hide everything under _WITH_CPU_SET_T, in particular, do not expose
sched_getcpu(), sched_get/setaffinity(), as well as CPU_* and BIT_*
macros.  Consumers that want sched* functions must opt-in.

Reported by:	portmgr (antoine)
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week

include/sched.h

@@ -32,12 +32,9 @@
 #include <sys/cdefs.h>
 #include <sys/types.h>
 #include <sys/sched.h>
-#if __BSD_VISIBLE
-#include <sys/cpuset.h>
-#endif /* __BSD_VISIBLE */
-
 #if __BSD_VISIBLE
 #ifdef _WITH_CPU_SET_T
+#include <sys/cpuset.h>
 struct _cpuset;
 typedef struct _cpuset cpu_set_t;
 #endif /* _WITH_CPU_SET_T */
@@ -45,9 +42,11 @@ typedef struct _cpuset cpu_set_t;
 
 __BEGIN_DECLS
 #if __BSD_VISIBLE
+#ifdef _WITH_CPU_SET_T
 int sched_getaffinity(pid_t pid, size_t cpusetsz, cpuset_t *cpuset);
 int sched_setaffinity(int pid, size_t cpusetsz, const cpuset_t *cpuset);
 int sched_getcpu(void);
+#endif /* _WITH_CPU_SET_T */
 #endif /* __BSD_VISIBLE */
 __END_DECLS
 

lib/libc/gen/sched_getaffinity.c

@@ -26,6 +26,7 @@
  * SUCH DAMAGE.
  */
 
+#define	_WITH_CPU_SET_T
 #include <sched.h>
 
 int

lib/libc/gen/sched_getcpu_gen.c

@@ -26,6 +26,7 @@
  * SUCH DAMAGE.
  */
 
+#define	_WITH_CPU_SET_T
 #include <sched.h>
 #include "libc_private.h"
 

lib/libc/gen/sched_setaffinity.c

@@ -26,6 +26,7 @@
  * SUCH DAMAGE.
  */
 
+#define	_WITH_CPU_SET_T
 #include <sched.h>
 
 int

lib/libc/x86/sys/sched_getcpu_x86.c

@@ -32,6 +32,7 @@
 #include <machine/sysarch.h>
 #include <x86/ifunc.h>
 #include <errno.h>
+#define	_WITH_CPU_SET_T
 #include <sched.h>
 #include "libc_private.h"