[PATCH 1/2] selftests/pid_namespace: fix building with clang-20

[Dmitry Antipov <dmantipov@xxxxxxxxx>]

When using 'make LLVM=1 W=1 -C tools/testing/selftests/pid_namespace'
with clang-20, I've noticed the following:

pid_max.c:42:8: error: call to undeclared function 'mount'; ISO
C99 and later do not support implicit function declarations
[-Wimplicit-function-declaration]
   42 |         ret = mount("", "/", NULL, MS_PRIVATE | MS_REC, 0);
      |               ^
pid_max.c:42:29: error: use of undeclared identifier 'MS_PRIVATE'
   42 |         ret = mount("", "/", NULL, MS_PRIVATE | MS_REC, 0);
      |                                    ^
...

So include '<sys/mount.h>' to add all of the required declarations.

Signed-off-by: Dmitry Antipov <dmantipov@xxxxxxxxx>
---
 tools/testing/selftests/pid_namespace/pid_max.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/testing/selftests/pid_namespace/pid_max.c b/tools/testing/selftests/pid_namespace/pid_max.c
index 51c414faabb0..972bedc475f1 100644
--- a/tools/testing/selftests/pid_namespace/pid_max.c
+++ b/tools/testing/selftests/pid_namespace/pid_max.c
@@ -11,6 +11,7 @@
 #include <string.h>
 #include <syscall.h>
 #include <sys/wait.h>
+#include <sys/mount.h>
 
 #include "../kselftest_harness.h"
 #include "../pidfd/pidfd.h"
-- 
2.48.1