[PATCH bpf-next v3] bpf: syscall_nrs: disable no previous prototype warnning

[Jason Xing <kerneljasonxing@gmail.com>]

From: Jason Xing <kernelxing@tencent.com>

In some environments (gcc treated as error in W=1, which is default), if we
make -C samples/bpf/, it will be stopped because of
"no previous prototype" error like this:

  ../samples/bpf/syscall_nrs.c:7:6:
  error: no previous prototype for ‘syscall_defines’ [-Werror=missing-prototypes]
   void syscall_defines(void)
        ^~~~~~~~~~~~~~~

Actually, this file meets our expectatations because it will be converted to
a .h file. In this way, it's correct. Considering the warnning stopping us
compiling, we can remove the warnning directly.

Signed-off-by: Jason Xing <kernelxing@tencent.com>
---
v3
Link: https://lore.kernel.org/all/20241001012540.39007-1-kerneljasonxing@gmail.com/
1. remove clang check (Andrii)
2. add matching pop at the bottom of that file (Andrii)

v2
Link: https://lore.kernel.org/all/CAEf4BzaVdr_0kQo=+jPLN++PvcU6pwTjaPVEA880kgDN94TZYw@mail.gmail.com/
1. use #pragma GCC diagnostic ignored to disable warnning (Andrii Nakryiko)
---
 samples/bpf/syscall_nrs.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/samples/bpf/syscall_nrs.c b/samples/bpf/syscall_nrs.c
index 88f940052450..a6e600f3d477 100644
--- a/samples/bpf/syscall_nrs.c
+++ b/samples/bpf/syscall_nrs.c
@@ -2,6 +2,9 @@
 #include <uapi/linux/unistd.h>
 #include <linux/kbuild.h>
 
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wmissing-prototypes"
+
 #define SYSNR(_NR) DEFINE(SYS ## _NR, _NR)
 
 void syscall_defines(void)
@@ -17,3 +20,5 @@ void syscall_defines(void)
 #endif
 
 }
+
+#pragma GCC diagnostic pop
-- 
2.37.3