Detect availability of <spawn.h> and posix_spawn function

configure

@@ -15578,6 +15578,24 @@ if test "x$ac_cv_func_execvpe" = xyes; then :
 fi
 
 
+## posix_spawn
+
+ac_fn_c_check_header_mongrel "$LINENO" "spawn.h" "ac_cv_header_spawn_h" "$ac_includes_default"
+if test "x$ac_cv_header_spawn_h" = xyes; then :
+  ac_fn_c_check_func "$LINENO" "posix_spawn" "ac_cv_func_posix_spawn"
+if test "x$ac_cv_func_posix_spawn" = xyes; then :
+  ac_fn_c_check_func "$LINENO" "posix_spawnp" "ac_cv_func_posix_spawnp"
+if test "x$ac_cv_func_posix_spawnp" = xyes; then :
+  $as_echo "#define HAS_POSIX_SPAWN 1" >>confdefs.h
+
+fi
+
+fi
+
+fi
+
+
+
 ## ffs or _BitScanForward
 
 ac_fn_c_check_func "$LINENO" "ffs" "ac_cv_func_ffs"

configure.ac

@@ -1559,6 +1559,12 @@ AC_CHECK_FUNC([getauxval], [AC_DEFINE([HAS_GETAUXVAL])])
 
 AC_CHECK_FUNC([execvpe], [AC_DEFINE([HAS_EXECVPE])])
 
+## posix_spawn
+
+AC_CHECK_HEADER([spawn.h],
+  [AC_CHECK_FUNC([posix_spawn],
+    [AC_CHECK_FUNC([posix_spawnp], [AC_DEFINE([HAS_POSIX_SPAWN])])])])
+
 ## ffs or _BitScanForward
 
 AC_CHECK_FUNC([ffs], [AC_DEFINE([HAS_FFS])])

runtime/caml/s.h.in

@@ -243,6 +243,8 @@
 
 #undef HAS_EXECVPE
 
+#undef HAS_POSIX_SPAWN
+
 #undef HAS_FFS
 #undef HAS_BITSCANFORWARD