Bump minimum cmake version to 3.28 to use `JOB_SERVER_AWARE` when calling the `test-vanilla` target (and also `docs-prepare` and `test-docs`, though it's not as important there).
Homebrew doesn't provide a merged (FHS) prefix and tools installed from
it cannot be expected to appear on PATH. Furthermore, XCode provides
some tools and headers (Flex, Bison) which must not be used if
a Homebrew alternative is installed.
This change uses the `find_program(VALIDATOR)` functionality available
since CMake 3.25 to find the acceptable Bison executable instead of
failing if the first one found is too old. (macOS ships with Bison 2.6.)
This change also explicitly finds a usable M4 and ensures the Bison
command will use it. (macOS ships with an m4 which can fail if XCode
Tools aren't installed.)
Make explicit the location for the `CMakeUserPresets.json` file.
Update docs tests documentation.
Move `BUILD_DIR` and `PROGRAM_PREFIX` comments into the functional tests todo.
Add cmake to MacPorts/FreeBSD install instructions.
Add ccache to example `CMakeUserPresets.json` (it isn't otherwise documented, and is no longer as obvious without an `ENABLE_CCACHE` makevar).
Addressing comments
Also skip calling `tail` on stubnets log outputs.
Fix auxprog prefixes
i.e. if we've set `YOSYS_PROGRAM_PREFIX=why`, we shouldn't be trying to call `build/yosys` when building docs (because if we've done a clean build it doesn't exist).
I suspect this also affects tests, but I was working on docs when I noticed it.
Pipes the help through sed for the tools that include the path. Also means we can drop the `|| true` from abc, since we're now reading the sed return instead.
