[CMake] enable the use of system fmt

[tdavidcl]

This pr enable the use of fmtlib provided by the host system instead of the one from the git submodule.
This should fix shamrock on most recent MacOs

[github-actions]

Workflow report

workflow report corresponding to commit 0811eb0
Commiter email is timothee.davidcleris@proton.me

Pre-commit check report

Pre-commit check: ✅

trim trailing whitespace.................................................Passed
fix end of files.........................................................Passed
check for merge conflicts................................................Passed
check that executables have shebangs.....................................Passed
check that scripts with shebangs are executable..........................Passed
check for added large files..............................................Passed
check for case conflicts.................................................Passed
check yaml...............................................................Passed
detect private key.......................................................Passed
Validate GitHub Workflows................................................Passed
clang-format.............................................................Passed
Check doxygen headers....................................................Passed
Check license headers....................................................Passed
Check #pragma once.......................................................Passed
Check SYCL #include......................................................Passed

Test pipeline can run.

Clang-tidy diff report

No relevant changes found.
Well done!

You should now go back to your normal life and enjoy a hopefully sunny day while waiting for the review.

Doxygen diff with main

Removed warnings : 2
New warnings : 2
Warnings count : 5564 → 5564 (0.0%)

Detailed changes :

- src/shamrock/src/legacy/patch/base/patchdata_field.cpp:121: warning: Member X(a) (macro definition) of file patchdata_field.cpp is not documented.
+ src/shamrock/src/legacy/patch/base/patchdata_field.cpp:125: warning: Member X(a) (macro definition) of file patchdata_field.cpp is not documented.
- src/shamsys/src/legacy/sycl_mpi_interop.cpp:272: warning: Member X(a) (macro definition) of file sycl_mpi_interop.cpp is not documented.
+ src/shamsys/src/legacy/sycl_mpi_interop.cpp:280: warning: Member X(a) (macro definition) of file sycl_mpi_interop.cpp is not documented.