configure: fix the check for unsigned time_t

Assign the time_t variable negative value and then check if it is
greater than zero, which will evaluate true for unsigned time_t but
false for signed time_t.

diff --git a/configure.ac b/configure.ac
index 76fa93d1baadd572fdfd5142345aa122142fbd06..d305e9693533ee0ecf2ca97bf690ff912f4e2c34 100755 (executable)
--- a/configure.ac
+++ b/configure.ac
@@ -3488,7 +3488,7 @@ AC_RUN_IFELSE([
   AC_LANG_SOURCE([[
   #include <time.h>
   #include <limits.h>
-  time_t t = ULONG_MAX;
+  time_t t = -1;
   return (t > 0);
   ]])] ,[
   AC_MSG_RESULT([yes])