Fix 'undefined symbol GC_arrays` in tools on Solaris

* tools/if_mach.c (NOT_GCBUILD): Define macro (before include
`gc_priv.h`).
* tools/if_not_there.c (NOT_GCBUILD): Likewise.
* tools/setjmp_t.c (NOT_GCBUILD): Likewise.
* tools/threadlibs.c [HAVE_CONFIG_H]: Include `config.h`.
* tools/threadlibs.c: Include `gcconfig.h` instead of `gc_priv.h`;
include `stdio.h`.

Author: ivmai

tools/if_mach.c

@@ -1,5 +1,6 @@
 /* Conditionally execute a command based on machine and OS from gcconfig.h */
 
+#define NOT_GCBUILD
 #include "private/gc_priv.h"
 
 #include <string.h>

tools/if_not_there.c

@@ -2,6 +2,7 @@
 /* does not exist.  If the command is omitted (and the file does not    */
 /* exist) then just exit with a non-zero code.                          */
 
+#define NOT_GCBUILD
 #include "private/gc_priv.h"
 
 #include <unistd.h>

tools/setjmp_t.c

@@ -22,6 +22,7 @@
 /* safe, but this will not be noticed by this piece of       */
 /* code.)  This test appears to be far from perfect.         */
 
+#define NOT_GCBUILD
 #include "private/gc_priv.h"
 
 #include <string.h>

tools/threadlibs.c

@@ -15,7 +15,13 @@
  * modified is included with the above copyright notice.
  */
 
-#include "private/gc_priv.h"
+#ifdef HAVE_CONFIG_H
+#  include "config.h"
+#endif
+
+#include "private/gcconfig.h"
+
+#include <stdio.h>
 
 int
 main(void)