libbpf: add v1.4.6, add cross-compilation support

[valgur]

Summary

Changes to recipe: lib/[version]

Motivation

Details

Switched from AutotoolsToolchain to GnuToolchain for tc.extra_env.vars(self)["CC"] info and better cross-compilation support overall. It might be possible to make it work with AutotoolsToolchain as well though.

Successfully builds with

[settings]
arch=armv8
build_type=Release
compiler=gcc
compiler.cppstd=gnu20
compiler.libcxx=libstdc++11
compiler.version=14
os=Linux

[conf]
tools.build:compiler_executables={'c': 'aarch64-linux-gnu-gcc-14', 'cpp': 'aarch64-linux-gnu-g++-14', 'strip': 'aarch64-linux-gnu-strip'}
tools.cmake.cmaketoolchain:user_toolchain=['/home/martin/.conan2/armv8_toolchain.cmake']

set(CMAKE_FIND_ROOT_PATH /usr/aarch64-linux-gnu) 
set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)

---

• Read the contributing guidelines
• Checked that this PR is not a duplicate: list of PRs by recipe
• Tested locally with at least one configuration using a recent version of Conan