Fix build failure on systems without spawn.h

configure.ac

@@ -639,6 +639,7 @@ AC_CHECK_HEADERS([mntent.h sys/mnttab.h sys/vfstab.h sys/mntctl.h fstab.h])
 AC_CHECK_HEADERS([linux/magic.h])
 AC_CHECK_HEADERS([termios.h])
 AC_CHECK_HEADERS([alloca.h])
+AC_CHECK_HEADERS([spawn.h])
 
 # Some versions of MSC lack these
 AC_CHECK_HEADERS([dirent.h sys/time.h])

glib/gspawn.c

@@ -30,7 +30,10 @@
 #include <string.h>
 #include <stdlib.h>   /* for fdwalk */
 #include <dirent.h>
+
+#ifdef HAVE_SPAWN_H
 #include <spawn.h>
+#endif /* HAVE_SPAWN_H */
 
 #ifdef HAVE_CRT_EXTERNS_H
 #include <crt_externs.h> /* for _NSGetEnviron */

meson.build

@@ -227,6 +227,7 @@ headers = [
   'poll.h',
   'pwd.h',
   'sched.h',
+  'spawn.h',
   'stdint.h',
   'stdlib.h',
   'string.h',