Userland: Tests: Use mkstemp temporary files in tests

Userland/Tests/Kernel/elf-execve-mmap-race.cpp

@@ -28,8 +28,10 @@
 #include <fcntl.h>
 #include <pthread.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 #include <sys/mman.h>
+#include <sys/stat.h>
 #include <sys/wait.h>
 #include <unistd.h>
 
@@ -95,9 +97,15 @@ int main()
 
     header.e_entry = 0;
 
-    int fd = open("/tmp/x", O_RDWR | O_CREAT, 0777);
+    char path[] = "/tmp/x.XXXXXX";
+    auto fd = mkstemp(path);
     if (fd < 0) {
-        perror("open");
+        perror("mkstemp");
+        return 1;
+    }
+
+    if (fchmod(fd, 0777) < 0) {
+        perror("chmod");
         return 1;
     }
 
@@ -143,7 +151,7 @@ int main()
         if (!fork()) {
         try_again:
             printf("exec\n");
-            if (execl("/tmp/x", "x", nullptr) < 0) {
+            if (execl(path, "x", nullptr) < 0) {
             }
             goto try_again;
         }