check Lua, even when using lua-config

stepmania/autoconf/m4/lua.m4

@@ -4,6 +4,23 @@ AC_CHECK_PROGS(LUA_CONFIG, [lua-config50 lua-config], "")
 if test "$LUA_CONFIG" != ""; then
 	LUA_CFLAGS=`$LUA_CONFIG --include`
 	LUA_LIBS=`$LUA_CONFIG --static`
+
+	old_LIBS=$LIBS
+	LIBS="$LIBS $LUA_LIBS"
+	
+	AC_CHECK_FUNC(lua_open, , LUA_MISSING=yes)
+
+	# If lua-config exists, we should at least have Lua; if it fails to build,
+	# something other than it not being installed is wrong.
+	if test "$LUA_MISSING" = "yes"; then
+		echo
+		echo "*** $LUA_CONFIG was found, but a Lua test program failed to build."
+		echo "*** Please check your installation."
+		exit 1;
+	fi
+	AC_CHECK_FUNC(luaopen_base, , LUA_LIB_MISSING=yes)
+
+	LIBS="$old_LIBS"
 else
 	if test "$LIB_LUA" = ""; then
 		AC_CHECK_LIB(lua, lua_open, LIB_LUA=-llua)
@@ -18,20 +35,27 @@ else
 		AC_CHECK_LIB(lualib50, luaopen_base, LIB_LUA_LIB=-llualib50, , [$LIB_LUA -ldl])
 	fi
 	if test "$LIB_LUA" = ""; then
-		echo
-		echo "*** liblua is required to build StepMania; please make sure that"
-		echo "*** it is installed to continue the installation process."
-		exit 0;
+		LUA_MISSING=yes
 	fi
 	if test "$LIB_LUA_LIB" = ""; then
-		echo
-		echo "*** liblualib is required to build StepMania; please make sure that"
-		echo "*** it is installed to continue the installation process."
-		exit 0;
+		LUA_LIB_MISSING=yes
 	fi
 	LUA_CFLAGS=
 	LUA_LIBS="$LIB_LUA $LIB_LUA_LIB"
 fi
+if test "$LUA_MISSING" = "yes"; then
+	echo
+	echo "*** liblua is required to build StepMania; please make sure that"
+	echo "*** it is installed to continue the installation process."
+	exit 1;
+fi
+if test "$LUA_LIB_MISSING" = "yes"; then
+	echo
+	echo "*** liblualib is required to build StepMania; please make sure that"
+	echo "*** it is installed to continue the installation process."
+	exit 1;
+fi
+
 AC_SUBST(LUA_CFLAGS)
 AC_SUBST(LUA_LIBS)