build: enable building for Fedora40 and Ubuntu 24.04

[pstorz]

Thank you for contributing to the Bareos Project!

Please check

• Short description and the purpose of this PR is present above this paragraph
• Your name is present in the AUTHORS file (optional)

If you have any questions or problems, please give a comment in the PR.

Helpful documentation and best practices

• Git Workflow
• Automatic Sourcecode Formatting
• Check your commit messages
• Boy Scout Rule

Checklist for the reviewer of the PR (will be processed by the Bareos team)

Make sure you check/merge the PR using devtools/pr-tool to have some simple automated checks run and a proper changelog record added.

General

• Is the PR title usable as CHANGELOG entry?
• Purpose of the PR is understood
• Commit descriptions are understandable and well formatted
• Required backport PRs have been created

Source code quality

• Source code changes are understandable
• Variable and function names are meaningful
• Code comments are correct (logically and spelling)
• Required documentation changes are present and part of the PR

Tests

• Decision taken that a test is required (if not, then remove this paragraph)
• The choice of the type of test (unit test or systemtest) is reasonable
• Testname matches exactly what is being tested
• On a fail, output of the test leads quickly to the origin of the fault

[arogge]

I have a few remarks concerning the CPM integration. But overall this looks good!

[arogge]

I guess it is sufficient to simply check if this was set and then force local packages only.
That way everybody can build in fully disconnected mode, but things will fail in a nice way (i.e. find_package() should throw an error).
In the meantime we will need to manually turn off FETCHCONTENT_FULLY_DISCONNECTED for some of the package managers.

Suggested change

	set(FETCHCONTENT_FULLY_DISCONNECTED CACHE STRING "OFF" FORCE)
	mark_as_advanced(FETCHCONTENT_FULLY_DISCONNECTED)
	if(FETCHCONTENT_FULLY_DISCONNECTED)
	message(WARNING "Detected FETCHCONTENT_FULLY_DISCONNECTED.")
	message(WARNING "As this will break fetching, only local packages will be considered!")
	set(CPM_LOCAL_PACKAGES_ONLY ON)
	endif()

However, this section should be moved after the include(CPM) so that CMake already knows CPM_LOCAL_PACKAGES_ONLY is an option.

As an alternative we could also decide to just fail with a bad combination of parameters:

if(FETCHCONTENT_FULLY_DISCONNECTED AND NOT CPM_LOCAL_PACKAGES_ONLY)
  message(FATAL_ERROR "When FETCHCONTENT_FULLY_DISCONNECTED is enabled, CPM_LOCAL_PACKAGES_ONLY must be enabled, too!")
endif()

[arogge]

Suggested change

	if(PS)
	set(PSCMD ${PS})
	if(${CMAKE_SYSTEM_NAME} MATCHES "Linux")
	set(PSCMD ${PS})
	if(${CMAKE_SYSTEM_NAME} MATCHES "Linux")

(adapt following lines, too)

[arogge]

this should go before find_program(PS).

[arogge]

If ps is optional for the build, but required for systemtests, it may make sense to leave this file as is, but to add find_program(PS ps REQUIRED) to systemtests/CMakeLists.txt so it is only actually required to build systemtests (i.e. not when building MacOS or a ULC).
CMake will not search the program twice, so it won't hurt.

[arogge]

we might want to unconditionally enable CPM_USE_LOCAL_PACKAGES so find_package() is always tried first:

Suggested change

	include(CPM)
	include(CPM)
	set(CPM_USE_LOCAL_PACKAGES ON)

[arogge]

You can add the package like this:

Suggested change

	CPMAddPackage("gh:fmtlib/fmt#10.2.1")
	CPMAddPackage(
	NAME fmt
	VERSION 6.2.1
	GITUB_REPOSITORY "fmtlib/fmt"
	GIT_TAG "10.2.1"
	EXCLUDE_FROM_ALL
	)

This will select any local version 6.2.1 or newer, if it exists, and will download and use 10.2.1 from GitHub otherwise.

However, the CMake-code for that should be in the toplevel CMakeLists.txt. Considering the amount of things we're probably going to add here, it may make sense to create an individual file and include() that from the toplevel CMakeLists.txt.