Благодарю!
Вся моя проблема была в отсутствии 2-ой строки.

export LUAJIT_INC=%{_includedir}/luajit-5_1-2.1
export LUAJIT_LIB=%{_libdir}

Видимо если переопределяю LUAJIT_INC то нужно сразу и переопределить LUAJIT_LIB даже если она стандартная.

Луамодуль собрал, буду собирать lua-resty-redis.

P.S. /var/log/nginx/error.log

2024/04/19 11:21:48 [alert] 23985#23985: detected a LuaJIT version which is not OpenResty's; many optimizations will be disabled and performance will be compromised (see https://github.com/openresty/luajit2 for OpenResty's LuaJIT or, even better, consider using the OpenResty releases from https://openresty.org/en/download.html)
2024/04/19 11:21:48 [alert] 23985#23985: failed to load the 'resty.core' module (https://github.com/openresty/lua-resty-core); ensure you are using an OpenResty release from https://openresty.org/en/download.html (reason: module 'resty.core' not found:
    no field package.preload['resty.core']
    no file './resty/core.lua'
    no file '/usr/share/luajit-5_1-2.1/resty/core.lua'
    no file '/usr/local/share/lua/5.1/resty/core.lua'
    no file '/usr/local/share/lua/5.1/resty/core/init.lua'
    no file '/usr/share/lua/5.1/resty/core.lua'
    no file '/usr/share/lua/5.1/resty/core/init.lua'
    no file './resty/core.so'
    no file '/usr/local/lib/lua/5.1/resty/core.so'
    no file '/usr/lib64/lua/5.1/resty/core.so'
    no file '/usr/local/lib/lua/5.1/loadall.so'
    no file './resty.so'
    no file '/usr/local/lib/lua/5.1/resty.so'
    no file '/usr/lib64/lua/5.1/resty.so'
    no file '/usr/local/lib/lua/5.1/loadall.so') in /etc/nginx/nginx.conf:67

Ещё и lua-resty-core нужен.