fix(concord-once): building on Cygwin

This fix is totally based off Anotra's PR commits #172, adapted to work on dev before the PR is merged.

Author: ThePedroo

src/concord-once.c

@@ -72,12 +72,16 @@ ccord_global_init()
         }
         for (int i = 0; i < 2; i++) {
             const int on = 1;
-            if (0 != ioctl(shutdown_fds[i], FIOCLEX, NULL)) {
-                fputs("Failed to make shutdown pipe close on execute\n",
-                      stderr);
-                goto fail_pipe_init;
-            }
-            if (0 != ioctl(shutdown_fds[i], FIONBIO, &on)) {
+
+            #ifdef FIOCLEX
+                if (0 != ioctl(shutdown_fds[i], FIOCLEX, NULL)) {
+                    fputs("Failed to make shutdown pipe close on execute\n",
+                        stderr);
+                    goto fail_pipe_init;
+                }
+            #endif
+
+            if (0 != ioctl(shutdown_fds[i], (int)FIONBIO, &on)) {
                 fputs("Failed to make shutdown pipe nonblocking\n", stderr);
                 goto fail_pipe_init;
             }
@@ -125,9 +129,17 @@ discord_dup_shutdown_fd(void)
     if (-1 == shutdown_fds[0]) return -1;
     if (-1 != (fd = dup(shutdown_fds[0]))) {
         const int on = 1;
-        if (0 != ioctl(fd, FIOCLEX, NULL) && 0 != ioctl(fd, FIONBIO, &on)) {
+
+        #ifdef FIOCLEX
+            if (0 != ioctl(fd, FIOCLEX, NULL)) {
+                close(fd);
+                return -1;
+            }
+        #endif
+
+        if (0 != ioctl(fd, (int)FIONBIO, &on)) {
             close(fd);
-            fd = -1;
+            return -1;
         }
     }
     return fd;