From eaf74df22f738b7ee8e65c6aaaa506e1a523e0f0 Mon Sep 17 00:00:00 2001
From: William S Fulton <wsf@fultondesigns.co.uk>
Date: Sat, 28 May 2016 10:37:19 +0100
Subject: [PATCH] Fix failure to detect lua.h on some systems

Fixes "present but cannot be compiled" autoconf failure looking for lua.h
---
 configure.ac | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index 2954d40b9..808ff21be 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2347,7 +2347,10 @@ if test "$LUABIN"; then
     AC_CHECK_FILE($LUAINCLUDE/lua.h,[LUAFLAGS="$ISYSTEM$LUAINCLUDE"],[LUABIN=])
   else
     LUA_OK="1"
-    AC_CHECK_HEADER(lua.h,[LUAFLAGS=""],[LUA_OK=""])
+    CFLAGS_SAVED=$CFLAGS
+    CFLAGS= # Use empty CFLAGS to avoid failure: "present but cannot be compiled"
+    AC_CHECK_HEADER([lua.h],[LUAFLAGS=""],[LUA_OK=""])
+    CFLAGS=$CFLAGS_SAVED
     # if we didn't get it, going to have to look elsewhere (the hard way)
     if test -z "$LUA_OK"; then
       AC_MSG_CHECKING(for lua.h in other locations)