cmake: BUILD_DEPS does not include a BUILD_SWIG option

[SYury]

What language and solver does this apply to?
CMake build

Describe the problem you are trying to solve.
I'm building OR-Tools Python package from source on an Ubuntu machine:

cmake -S. -Bbuild -DBUILD_DEPS:BOOL=ON -DBUILD_PYTHON=ON -DCMAKE_BUILD_TYPE=Release

I don't have the rights to install packages from apt, so I build the dependencies from source.

Everything is ok when I build the C++ library without Python, but when I build the Python package it fails with Could NOT find SWIG (missing: SWIG_EXECUTABLE SWIG_DIR). Apparently, BUILD_DEPS does not include SWIG.

Describe the solution you'd like
Fetch and build SWIG from source when both BUILD_DEPS and BUILD_PYTHON are on.

[lperron]

Unsure.

There are other things you need to install anyway, python-dev for instance, that are not installed by default.

So I am not convinced this will enable sudo-less builds

[Mizux]

seems SWIG has a cmake based build
ref: https://github.com/swig/swig/blob/master/CMakeLists.txt

Need to add it to the todo list for 2042 or beyond ^^;

note: may need to try to add it to https://mizux.dev/python-native to fast iterate on the dev then bakcport to or-tools once ready

ps: BUILD_PYTHON set BUILD_DEPS to ON by default, so don't need to specify both ;)
aka by default we prefer to provide a standalone wrapper package (note: we also build every deps as statis lib to avoid to ship dozen of .so + windows don't support RUNPATH..)

or-tools/CMakeLists.txt

Lines 161 to 167 in 528badf

	# By default all dependencies are NOT built (i.e. BUILD_DEPS=OFF),
	# BUT if building any wrappers (Python, Java or .Net) then BUILD_DEPS=ON.
	if(BUILD_PYTHON OR BUILD_JAVA OR BUILD_DOTNET)
	option(BUILD_DEPS "Build all dependencies" ON)
	else()
	option(BUILD_DEPS "Build all dependencies" OFF)
	endif()

also

or-tools/CMakeLists.txt

Lines 49 to 53 in 528badf

	if(NOT CMAKE_BUILD_TYPE)
	set(CMAKE_BUILD_TYPE "Release" CACHE STRING
	"Choose the type of build, options are: Debug Release RelWithDebInfo MinSizeRel. (default: Release)"
	FORCE)
	endif()