enable luajit on the docker image

[BuckarooBanzay]

Overview

This PR adds luajit to the "stock" minetest docker image.

It will allow faster lua execution through the luajit library.

There are 2 stages in the Dockerfile: build and package.
In the build stage the luajit-dev package is pulled in with all the libraries and headers.
In the package stage only the luajit package with the previously linked libraries is included.
The size-increase is around 800 kb.

Stats

In my tests i had a 20x to 30x decrease in processing time for lua mapgens with jit enabled.

State

This PR is Ready for Review.

How to test

# buid the image locally
docker build . -t minetest-jit

# start the server part with the new image
docker run --rm -it --network host minetest-jit

# connect with a client to 127.0.0.1:30000
# everything should work as before (or faster)

[paramat]

It will allow faster lua execution through the luajit library.

In my tests i had a 20x to 30x decrease in processing time for lua mapgens with jit enabled.

I am confused, we can already use LuaJIT so why is the increase in Lua speed stated as a benefit of this PR?
The presentation of the PR seems to imply LuaJIT is forced to operate at all times, LuaJIT must remain optional.
Some of the more intensive Lua mapgens and Lua mods are incompatible with LuaJIT because it causes OOM crashes.

[sfan5]

This is solely for the docker image we provide (see here), it doesn't change anything about the build process or what is/isn't required.

[nerzhul]

Are you sure we use it on build ? you just install package, we don't have options to pass to cmake ?

[BuckarooBanzay]

Are you sure we use it on build ? you just install package, we don't have options to pass to cmake ?

It's auto-detected:

Step 21/30 : RUN mkdir build && 	cd build && 	cmake .. 		-DCMAKE_INSTALL_PREFIX=/usr/local 		-DCMAKE_BUILD_TYPE=Release 		-DBUILD_SERVER=TRUE 		-DENABLE_PROMETHEUS=TRUE 		-DBUILD_UNITTESTS=FALSE 	-DBUILD_CLIENT=FALSE && 	make -j2 && 	make install
 ---> Running in fdeb2f66a395
-- The C compiler identification is GNU 9.3.0
-- The CXX compiler identification is GNU 9.3.0
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- *** Will build version 5.4.0-dev ***
-- Found Irrlicht: /usr/lib/libIrrlicht.so  
-- Using GMP provided by system.
-- Found GMP: /usr/lib/libgmp.so  
-- Using bundled JSONCPP library.
-- Found LuaJIT: /usr/lib/libluajit-5.1.so (found version "") 
-- Using LuaJIT provided by system.

[HybridDog]

As far as I know, there are bugfixes in the latest luajit which are not included in the latest stable release, for example: LuaJIT/LuaJIT@45a7e50
Does it install the latest LuaJIT or the relatively old LuaJIT 2.1.0-beta3 from 2017?

[BuckarooBanzay]

As far as I know, there are bugfixes in the latest luajit which are not included in the latest stable release, for example: LuaJIT/LuaJIT@45a7e50
Does it install the latest LuaJIT or the relatively old LuaJIT 2.1.0-beta3 from 2017?

It installs 2.1.0_beta3-r6

[SmallJoker]

LGTM