Even though I have LuaJIT installed, the rpm fails to build for me on CentOS 7.
$ rpm -qa luajit
luajit-2.0.4-3.el7.x86_64
[...]
configuring additional modules
adding module in ./ngx_devel_kit
+ ngx_devel_kit was configured
configuring additional dynamic modules
adding module in ./lua-nginx-module
checking for LuaJIT library in /usr/lib64 and /usr/include/luajit-2.1 (specified by the LUAJIT_LIB and LUAJIT_INC env, with -ldl) ... found
checking for LuaJIT 2.x ... not found
./configure: error: unsupported LuaJIT version; ngx_http_lua_module requires LuaJIT 2.x.
error: Bad exit status from /var/tmp/rpm-tmp.MjKdeF (%build)