build-sys:

While the previous commit checked for a GNU environment so Hurd
compilied ok, this tripped up Cygwin. configure now explicitly tests
for the structure field rather than trying to guess through compilier
flags about what the environment tells us about signals.h

References:
 commit d39d9db079

Signed-off-by: Craig Small <csmall@dropbear.xyz>

configure.ac

@@ -69,6 +69,7 @@ AC_C_RESTRICT
 AC_TYPE_SIZE_T
 AC_TYPE_SSIZE_T
 AC_CHECK_MEMBERS([struct stat.st_rdev])
+AC_CHECK_MEMBERS([siginfo_t.si_int], [], [], [[#include <signal.h>]])
 
 dnl libtool
 LT_INIT

lib/test_process.c

@@ -62,7 +62,7 @@ signal_handler(int signum, siginfo_t *siginfo, void *ucontext)
 	    printf("SIG %s\n", signame);
 	    break;
 	case SI_QUEUE:
-#	    ifndef __GNU__
+#ifdef HAVE_SIGINFO_T_SI_INT
 	        printf("SIG %s value=%d\n", signame, siginfo->si_int);
 #else
 	        printf("case SI_QUEUE: SIG %s siginfo->si_int undefined\n", signame);