Adjust installation location to /usr.

Upstream: N/A specific for Buildroot build
Signed-off-by: Francois Perrad <francois.perrad@gadz.org>

Index: b/src/luaconf.h
===================================================================
--- a/src/luaconf.h
+++ b/src/luaconf.h
@@ -223,7 +223,7 @@
 
 #else			/* }{ */
 
-#define LUA_ROOT	"/usr/local/"
+#define LUA_ROOT	"/usr/"
 #define LUA_LDIR	LUA_ROOT "share/lua/" LUA_VDIR "/"
 #define LUA_CDIR	LUA_ROOT "lib/lua/" LUA_VDIR "/"