[BUGFIX PATCH] selftests/x86: Check the availablity of sys/syscall.h

[Masami Hiramatsu <mhiramat@kernel.org>]

Since single_step_syscall.c depends on sys/syscall.h and
its include, asm/unistd.h, we should check the availability
of those headers.
Without this fix, if gcc-multilib is not installed but
libc6-dev-i386 is installed, kselftest tries to build 32bit
binary and failed with following error message.

In file included from single_step_syscall.c:18:
/usr/include/sys/syscall.h:24:10: fatal error: asm/unistd.h: No such file or directory
 #include <asm/unistd.h>
          ^~~~~~~~~~~~~~
compilation terminated.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 .../testing/selftests/x86/trivial_32bit_program.c  |    1 +
 .../testing/selftests/x86/trivial_64bit_program.c  |    1 +
 2 files changed, 2 insertions(+)

diff --git a/tools/testing/selftests/x86/trivial_32bit_program.c b/tools/testing/selftests/x86/trivial_32bit_program.c
index aa1f58c2f71c..6b455eda24f7 100644
--- a/tools/testing/selftests/x86/trivial_32bit_program.c
+++ b/tools/testing/selftests/x86/trivial_32bit_program.c
@@ -8,6 +8,7 @@
 # error wrong architecture
 #endif
 
+#include <sys/syscall.h>
 #include <stdio.h>
 
 int main()
diff --git a/tools/testing/selftests/x86/trivial_64bit_program.c b/tools/testing/selftests/x86/trivial_64bit_program.c
index 39f4b84fbf15..07ae86df18ff 100644
--- a/tools/testing/selftests/x86/trivial_64bit_program.c
+++ b/tools/testing/selftests/x86/trivial_64bit_program.c
@@ -8,6 +8,7 @@
 # error wrong architecture
 #endif
 
+#include <sys/syscall.h>
 #include <stdio.h>
 
 int main()