Improve build process

[D-mo]

Current situation:

1. Currently the build process involves fetching Lua, zlib and possibly other things from the Internet.

   So, every time someone wants to do a clean build, these packages have to be re-downloaded. This is a waste of time and electrons. Also, if a person is offline, they can't even do a build.

2. The above dependencies (Lua, zlib, etc.) are located in external repositories. This means if the author decides to take it down or move it, the build process is snafu.

Therefore, I would like to propose the following:

1. The external dependencies become git submodules, so they can be fetched once with the Orbiter and don't have to re-downloaded on each clean build.

2. These submodules should be cloned into orbitersim first, and Orbiter should depend on the local clones.

[D-mo]

The dependencies I've identified are:

• Lua
  

  orbiter/Extern/lua/CMakeLists.txt

  Lines 5 to 9 in f3feab8

   FetchContent_Declare( 
     lua 
     GIT_REPOSITORY https://github.com/lua/lua.git 
     GIT_TAG v5.1 
   ) 

• zlib
  

  orbiter/Extern/zlib/CMakeLists.txt

  Lines 5 to 9 in f3feab8

   FetchContent_Declare( 
     zlib 
     GIT_REPOSITORY https://github.com/madler/zlib.git 
     GIT_TAG v1.2.11 
   ) 

• Catch2
  

  orbiter/Tests/CMakeLists.txt

  Lines 3 to 7 in f3feab8

   FetchContent_Declare( 
     Catch2 
     GIT_REPOSITORY https://github.com/catchorg/Catch2.git 
     GIT_TAG        v3.0.0-preview3 
   ) 

There are also binary deps, which are already part of Orbiter:

• HtmlHelp
• DirectX7 SDK.

And there is irrKlang which is used by XRsound:

orbiter/Sound/XRSound/CMakeLists.txt

Lines 3 to 22 in f3feab8

 if (IRRKLANG_DOWNLOAD) 
 	# Try downloading the irrKlang library on the fly 
 	set(IRRKLANG_DOWNLOAD_DIR ${ORBITER_BINARY_ROOT_DIR}/Extern/irrKlang/${ARCH}/) 
 	if (BUILD64) 
 		set(IRRKLANG_URL "https://www.ambiera.at/downloads/irrKlang-64bit-1.6.0.zip") 
 		set(IRRKLANG_DIR ${IRRKLANG_DOWNLOAD_DIR}/irrKlang-64bit-1.6.0) 
 	else() 
 		set(IRRKLANG_URL "https://www.ambiera.at/downloads/irrKlang-32bit-1.6.0.zip") 
 		set(IRRKLANG_DIR ${IRRKLANG_DOWNLOAD_DIR}/irrKlang-1.6.0) 
 	endif() 
 	if (EXISTS ${IRRKLANG_DIR}) 
 		message(STATUS "Found a previously downloaded irrKlang package.") 
 	else() 
 		message(STATUS "Downloading irrKlang ...") 
 		file(MAKE_DIRECTORY ${IRRKLANG_DOWNLOAD_DIR}) 
 		file(DOWNLOAD ${IRRKLANG_URL} ${IRRKLANG_DOWNLOAD_DIR}/irrKlang.zip) 
 		file(ARCHIVE_EXTRACT INPUT ${IRRKLANG_DOWNLOAD_DIR}/irrKlang.zip 
 			DESTINATION ${IRRKLANG_DOWNLOAD_DIR}) 
 	endif() 
 endif() 

[D-mo]

As a first step, could someone with write-access to orbitersim please fork the following repos:

• Lua: https://github.com/lua/lua.git
• zlib: https://github.com/madler/zlib.git
• Catch2: https://github.com/catchorg/Catch2.git

Next, we will try to turn them into submodules.

[D-mo]

I've submitted PR #347 which converts Lua, zlib and Catch2 into submodules.

@Xyon and/or @dbeachy1 if one of you could please fork the above 3 repos, we can change the submodules to point to local forks instead. This will guarantee continuity of the species in case any of those repos go offline in the future.

[D-mo]

PR #347 was merged. Closing.