memfd: Test for __NR_memfd_create during building

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

Makefile.config

@@ -41,6 +41,9 @@ endif
 ifeq ($(call try-cc,$(SETPROCTITLE_INIT_TEST),-lbsd),y)
 	$(Q) @echo '#define CONFIG_HAS_SETPROCTITLE_INIT' >> $@
 endif
+ifeq ($(call try-cc,$(MEMFD_TEST),),y)
+	$(Q) @echo '#define CONFIG_HAS_MEMFD' >> $@
+endif
 ifeq ($(piegen-y),y)
 	$(Q) @echo '#define CONFIG_PIEGEN' >> $@
 endif

scripts/feature-tests.mak

@@ -92,3 +92,17 @@ int main(int argc, char *argv[], char *envp[])
 }
 
 endef
+
+define MEMFD_TEST
+
+#include <unistd.h>
+#include <sys/syscall.h>
+
+int main(void)
+{
+#ifdef __NR_memfd_create
+	return 0;
+#endif
+}
+
+endef