Fix required CMake version

[Flamefire]

cxx_std_11 requires CMake 3.8

[Lastique]

cxx_std_11 is not used in Boost.Log. Why is this needed?

[Flamefire]

You are right, I was going by the error message: https://github.com/Flamefire/cmake/actions/runs/18138718785/job/51623991053#step:8:1792

CMake Error in libs/log/CMakeLists.txt:
Specified unknown feature "cxx_std_11" for target "boost_log_setup".

It seems CMake reports this when it was "inherited" too. I.e. some dependency sets this feature, with target_link_libraries it gets added to boost_log during the configure step and the generation step then trips over it.

So while this is (currently) not strictly required here in practice it is a requirement.

BTW: It should actually be used here. 2352b7e declares the library as C++11 and the Jamfile has the requirement too.

[Lastique]

It should actually be used here.

C++11 features are requested here:

log/CMakeLists.txt

Lines 462 to 467 in 3ab24d1

	target_compile_features(boost_log
	PUBLIC
	cxx_static_assert
	PRIVATE
	cxx_lambdas
	)

log/CMakeLists.txt

Lines 615 to 621 in 3ab24d1

	target_compile_features(boost_log_setup
	PUBLIC
	cxx_static_assert
	cxx_uniform_initialization
	PRIVATE
	cxx_lambdas
	)

Thanks for the fix.