std_thread_test doesn’t compile with the macOS 12 SDK due to conflicts with the native std::thread implementation. As this functionality is deprecated anyway, just disable the test.

…r with different allocator type"

The function is deprecated, so removal should not pose a problem.

This fixes a compiler error in Visual Studio 2017

The explicit invocation of ${CMAKE_CXX_COMPILER} to generate lists of
exported symbols was not taking into account the target architecture;
instead it would inherit whatever architecture was running the actual
build process. This could cause missing symbol errors when building the
macOS arm64 target from an x86_64 shell session.

…ICIT_LINKAGE

There was a quoting error in fd76ffb which meant the space between -arch
and the architecture was escaped. Also this commit adds the stdlib
argument to suppress a warning about the failure to find libstdc++, which
has not been available on macOS for some time.

Newer GCCs do not allow the meaning of "task" to change in the scope of
a class declaration, which is apparently invalid C++.