boost: Fix path finder for python libraries

[Minimonium]

Specify library name and version: boost/all

Fixes #2973

---

• I've read the guidelines for contributing.
• I've followed the PEP8 style guides for Python code in the recipes.
• I've used the latest Conan client version.
• I've tried at least one configuration locally with the
  conan-center hook activated.

[ghost]

I detected other pull requests that are modifying boost/all recipe:

• boost: Port patches from 1.77.0 to 1.78.0 #9106
• (#9047) boost: Bump build_requires of 'b2' to '4.7.1' (was '4.5.0') #9069
• [boost] Apply patch to fix https://github.com/boostorg/graph/issues/268 #6132
• boost: use clang-win toolset when compiler=Visual Studio and compiler.toolset=ClangCL #4749

This message is automatically generated by https://github.com/ericLemanissier/conan-center-conflicting-prs so don't hesitate to report issues/improvements there.

[SSE4]

/cc @grafikrobot

I don't remember all the details of how boost.python finds python libraries, it will require checking the docs and code, I only recall it was very cryptic, and AFAIK it requires a full path to the python library (otherwise, how did it know which one to pick if there are several variants in the same directory, like debug/release or static/shared).

[prince-chrismc]

I recall a few PRs from @madebr trying to sort this out as well... there's too many issues and PRs I wasnt able to find anything 😖

[madebr]

That function is used here

conan-center-index/recipes/boost/all/conanfile.py

Lines 1188 to 1194 in 89e6169

	if not self.options.without_python:
	# https://www.boost.org/doc/libs/1_70_0/libs/python/doc/html/building/configuring_boost_build.html
	contents += '\nusing python : {version} : "{executable}" : "{includes}" : "{libraries}" ;'\
	.format(version=self._python_version,
	executable=self._python_executable,
	includes=self._python_includes,
	libraries=self._python_libraries)

I think that function is misnamed, it should be called _python_library_dirs or something similar.

[SSE4]

reading https://github.com/boostorg/build/blob/ae1b579606d06b8d8900fe65fd63dffb46647588/src/tools/python.jam, it seems like it is indeed a library directory, not a path to the library file. @grafikrobot can you confirm?

[conan-center-bot]

All green in build 2 (79527885987f60e2ba82f608804556a7de02d0a8):

• boost/1.77.0@:
  All packages built successfully! (All logs)

• boost/1.72.0@:
  All packages built successfully! (All logs)

• boost/1.70.0@:
  All packages built successfully! (All logs)

• boost/1.69.0@:
  All packages built successfully! (All logs)

• boost/1.73.0@:
  All packages built successfully! (All logs)

• boost/1.76.0@:
  All packages built successfully! (All logs)

• boost/1.75.0@:
  All packages built successfully! (All logs)

• boost/1.74.0@:
  All packages built successfully! (All logs)

• boost/1.78.0@:
  All packages built successfully! (All logs)

• boost/1.71.0@:
  All packages built successfully! (All logs)

[SSE4]

let's move forward. If I have some time, I'll run some tests with python on different platforms, but no promises.