CMake plumbing to build tls_edit

[illwieckz]

CMake plumbing to build tls_edit.

Requires:

• CMake plumbing to build the loader (2) #14

To build it, use src/tools/tls_edit as CMake source dir, not the main one building the loader.

[slipher]

Could this be made a stand-alone pull request? There is a force_tls_edit scons argument to use an externally-built tls_edit, so I would be able to validate this against the tests and approve quickly. Unlike the loader MinGW build which is still far from building correctly.

[slipher]

Note that #46 fixes some errors/warnings in the host-mode bits.

[illwieckz]

Could this be made a stand-alone pull request? There is a force_tls_edit scons argument to use an externally-built tls_edit, so I would be able to validate this against the tests and approve quickly. Unlike the loader MinGW build which is still far from building correctly.

It would be hard to do. This is small because it's written over all the other plumbing. While it is written to be built as a standalone build (this is a host tool), it leverages the rest of the CMake plumbing, and the shared libs (like platform) are built using the same CMake script as the loader. This is also done to keep close to what SCons did.

[illwieckz]

Just to make it obvious, one can build the tls_edit tool this way:

cmake -S src/tools/tls_edit -B build-tls-edit
cmake --build build-tls-edit

This reuses some of the CMake work done in #14, but this is a standalone build.

This PR is not standalone, but the build is.

The root CMake configuration from #14 doesn't build the tls_edit tool even with those patches. If in the future we want it to be, it will be done as a CMake ExternalProject with the ability to use a different compiler (since it's a host tool). Though I do believe it's better to build it as part of the Saigo toolchain instead.