fix(tests): fix UB in mk{fifo,nod,nodat}

Memory chunk is allocated with `malloc` and used as the `dest` buffer
for `strncat`. The `dest` argument in `strncat` has to be NUL terminated,
however it was not.

This commit fixes this issue in mk{fifo,nod,noat}.c.

Almost all dynamic tests pass now.

Signed-off-by: Anhad Singh <andypython@protonmail.com>

tests/mkfifo.c

@@ -11,7 +11,9 @@ int main(void) {
   char temp[] = "/tmp/stattest-XXXXXX";
   const char file[] = "/mkfifo_fifo";
   int len = sizeof(temp) + sizeof(file);
+
   char* path = malloc(len * sizeof(char));
+  path[0] = '\0';
 
   if (path == NULL) {
     fprintf(stderr, "Could not allocate: %s\n", strerror(errno));

tests/mknod.c

@@ -11,7 +11,9 @@ int main(void) {
   char temp[] = "/tmp/stattest-XXXXXX";
   const char file[] = "/mknod";
   int len = sizeof(temp) + sizeof(file);
+
   char* path = malloc(len * sizeof(char));
+  path[0] = '\0';
 
   if (path == NULL) {
     fprintf(stderr, "Could not allocate: %s\n", strerror(errno));

tests/mknodat.c

@@ -12,7 +12,9 @@ int main(void) {
   const char separator[] = "/";
   const char file[] = "mknod"; // relative
   int len = sizeof(temp) + sizeof(file) + sizeof(separator);
+
   char* path = malloc(len * sizeof(char));
+  path[0] = '\0';
 
   if (path == NULL) {
     fprintf(stderr, "Could not allocate: %s\n", strerror(errno));