[OpenMP][Obvious] Fix incompatbile function prototype causing failures

Summary:
This function needs `void` as the arguments to be ABI compatbile with
what is actually defined. This is enforced when doing CUDA separable
linking of the runtime.

openmp/libomptarget/test/api/omp_get_num_procs.c

@@ -2,7 +2,7 @@
 
 #include <stdio.h>
 
-int omp_get_num_procs();
+int omp_get_num_procs(void);
 
 int main() {
   int num_procs;