Update the newly-added unit test to compile with the new strict prototype flag.

tests/testEOS.c

@@ -274,5 +274,5 @@ int main(int argc, char *argv[]) {
   return 0;
 }
 #else
-int main() { return 0; }
+int main(int argc, char *argv[]) { return 0; }
 #endif

tests/testFFT.c

@@ -35,7 +35,6 @@ int main(int argc, char *argv[]) { return 0; }
 #include "runner_doiact_fft.h"
 #include "swift.h"
 
-
 __attribute__((always_inline)) INLINE static int row_major_id(int i, int j,
                                                               int k, int N) {
   return (((i + N) % N) * N * N + ((j + N) % N) * N + ((k + N) % N));

tests/testInteractions.c

@@ -748,6 +748,6 @@ int main(int argc, char *argv[]) {
 
 #else
 
-int main() { return 1; }
+int main(int argc, char *argv[]) { return 1; }
 
 #endif

tests/testKernelGrav.c

@@ -58,7 +58,7 @@ float gadget(float r, float epsilon) {
   }
 }
 
-int main() {
+int main(int argc, char *argv[]) {
 
   const float h = 3.f;
   const float r_max = 6.f;

tests/testUtilities.c

@@ -23,7 +23,7 @@
 /**
  * @brief Test generic utility functions
  */
-int main() {
+int main(int argc, char *argv[]) {
   /// Test find_value_in_monot_incr_array()
   int n = 100;
   float array[n];