chore: add ADA_TOOLS option

[myd7349]

This patch adds a new ADA_TOOLS option to allow users enable/disable the build of ada cli tools (adaparse) manually.

When trying to add a new port for ada-url in vcpkg, I found it failed to build adaparse on UWP: microsoft/vcpkg#31485 .

adaparse uses fmt::output_file defined in fmt/os.h. However, since UWP doesn't provide _pipe, FMT_USE_FCNTL is defined as 0, which in turn means fmt::output_file does not exist.

https://github.com/fmtlib/fmt/blob/master/include/fmt/os.h#L23

[anonrig]

We'll release v2.4.2 when this PR is merged. Thanks for your contribution @myd7349

[myd7349]

How about?

if(NOT ADA_COVERAGE AND NOT EMSCRIPTEN)
  add_subdirectory(singleheader)
endif()

if(ADA_TOOLS)
  add_subdirectory(tools)
endif()

[lemire]

@myd7349 Yes. That looks good.