erts: Eliminate warnings in C code in tests

Apple Clang 12 in Xcode 12 reports an error for the use of a
function without a declaration.

erts/emulator/test/driver_SUITE_data/peek_non_existing_queue_drv.c

@@ -47,6 +47,10 @@
 #include <windows.h>
 #endif
 
+#ifdef HAVE_UNISTD_H
+#   include <unistd.h>
+#endif
+
 #include <errno.h>
 
 #include "erl_driver.h"

erts/emulator/test/driver_SUITE_data/thr_msg_blast_drv.c

@@ -18,6 +18,10 @@
  * %CopyrightEnd%
  */
 
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+
 #include "erl_driver.h"
 
 #define THR_MSG_BLAST_NO_PROCS 10

erts/emulator/test/estone_SUITE_data/estone_cat.c

@@ -12,9 +12,11 @@
 #include <fcntl.h>
 #include <errno.h>
 
-main(argc, argv)
-int argc;
-char *argv[];
+#ifdef HAVE_UNISTD_H
+#   include <unistd.h>
+#endif
+
+int main(int argc, char* argv[])
 {
     char buf[16384];
     int n;

erts/emulator/test/mtx_SUITE_data/mtx_SUITE.c

@@ -39,6 +39,7 @@
 
 #include <errno.h>
 #include <stdio.h>
+#include <string.h>
 
 static int
 fail(const char *file, int line, const char *function, const char *assertion);

erts/emulator/test/port_bif_SUITE_data/port_test.c

@@ -10,6 +10,7 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
+#include <ctype.h>
 
 #ifndef __WIN32__
 #include <unistd.h>
@@ -32,7 +33,7 @@
     exit(1); \
 }
 
-#define MAIN(argc, argv) main(argc, argv)
+#define MAIN(argc, argv) int main(argc, argv)
 
 extern int errno;