Build documentation: a couple of minor issues

[pcanal]

This issue is regarding the content directly or indirectly from https://github.com/Framework-R-D/phlex/tree/main/scripts

The text mention 'graceful degradation' and mention that it will warn if there are missing tools. A misinterpretation on my part was the extent of tool, which accurately is only talking about the externally needed tools but is not reporting any missing dependencies (or 'tools') that are missing (eg boost, jsonnet, etc.). When following the instructions, those will be mentioned only when the CMake fails step. We get the needed information but need to repeat the configure step to discover each dependencies. A list or a link to the list of required (and optional) dependency would enhance the documentation. (The information is ex-tractable from https://github.com/Framework-R-D/phlex-spack-recipes.git )

The script scripts/setup-env.sh ends with the nice:

[Phlex Setup] To configure and build the project:
[Phlex Setup]   cmake --preset default -S /home/pcanal/phlex_working/code/phlex -B /exp/projects/root/phlex/build/2025-12
[Phlex Setup]   ninja -C /exp/projects/root/phlex/build/2025-12

However the last line is unchanged whether the configuration creates a ninja area or a Makefile area. (Setting CMAKE_GENERATOR outside the script has the desired effect, so simply setting it to Ninja make the script command work). An option might be to recommend cmake --build instead..