Arm Compiler for Linux support

[green-br]

Describe the bug
When building with the Arm Compiler for Linux CMake complains with:

CMake Warning at cmake/CompilerConfiguration.cmake:39 (message):
  Unknown Fortran compiler, trying without any additional (optimization)
  flags.

  You will most likely have to specify extra options for free-form Fortran
  2008 for your compiler!

  Please open an issue at https://github.com/cp2k/dbcsr/issues with the
  reported compiler name and the required flags.
Call Stack (most recent call first):
  CMakeLists.txt:340 (include)


-- CMAKE_Fortran_COMPILER_ID: Flang

To Reproduce
Steps to reproduce the behavior:

1. Built with the command: 'spack install cp2k@2024.3 %arm@24.10.1'
2. Run like this: (build-only failure)
3. On the architecture/host/platform: 'aarch64, Nvidia Grace CPU Superchip, SLES15sp5'
4. See error

Expected behavior
I expect CMake to detect the compiler and use the appropriate flags. Likely to be similar to LLVMFlang (but -std is not an option from look of manual):

set(CMAKE_Fortran_FLAGS          "${CMAKE_Fortran_FLAGS} -ffree-form -cpp")
set(CMAKE_Fortran_FLAGS_RELEASE  "-O3")
set(CMAKE_Fortran_FLAGS_DEBUG    "-O0 -g")

Environment:

• Operating system & version - SLES15sp5
• Compiler vendor & version - Arm Compiler for Linux 24.10
• Build environment (make or cmake) - cmake
• Configuration of DBCSR (either the cmake flags or the Makefile.inc) - generated by Spack for CP2K install.
• MPI implementation and version - OpenMPI 5.0.8
• If CUDA is being used: CUDA version and GPU architecture - not used
• BLAS/LAPACK implementation and version - in-built into Arm Compiler for Linux
• If applicable: Runtime information (how many nodes, type of nodes, ...)

[alazzaro]

Sorry for the late reply, we don't have access to ARM Flang, so we cannot try it. However, I've added the lines you suggested to the current develop branch (see f2e0d07 )
Note that in the past, we have tried FLANG (see flang-compiler/flang#239). I've just tried (flang-new version 20.0.0git) and I see the same error report by @dev-zero , despite the ticket reports that the problem was fixed long time ago...

Let me know if it works in your case.