samples/seccomp: Fix 32-bit build

Both the .o and the actual executable need to be built with -m32 in order
to link correctly.
Reported-by: NIngo Molnar <mingo@kernel.org>
Signed-off-by: NTycho Andersen <tycho@tycho.ws>
Reviewed-by: NKees Cook <keescook@chromium.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: James Morris <jmorris@namei.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: fec7b669 ("samples: add an example of seccomp user trap")
Link: http://lkml.kernel.org/r/20190107231631.1849-1-tycho@tycho.wsSigned-off-by: NIngo Molnar <mingo@kernel.org>

samples/seccomp/Makefile

@@ -34,6 +34,7 @@ HOSTCFLAGS_bpf-direct.o += $(MFLAG)
 HOSTCFLAGS_dropper.o += $(MFLAG)
 HOSTCFLAGS_bpf-helper.o += $(MFLAG)
 HOSTCFLAGS_bpf-fancy.o += $(MFLAG)
+HOSTCFLAGS_user-trap.o += $(MFLAG)
 HOSTLDLIBS_bpf-direct += $(MFLAG)
 HOSTLDLIBS_bpf-fancy += $(MFLAG)
 HOSTLDLIBS_dropper += $(MFLAG)