Incorrect compiler env variables if different compiler versions are installed

[hiker]

My wsl system had gcc-9 (only, no gfortran), and a full gcc-11* installed. The environmet created the following env variables:

CC=$'/usr/bin/gcc-9\n/usr/bin/gcc'
OMPI_CC=$'/usr/bin/gcc-9\n/usr/bin/gcc'
FC=$'None\n/usr/bin/gfortran'
OMPI_FC=$'None\n/usr/bin/gfortran'

Reason is the following output of spack compiler info:

RUN spack compiler info gcc
gcc@9.5.0:
        paths:
                cc = /usr/bin/gcc-9
                cxx = None
                f77 = None
                fc = None
        modules  = []
        operating system  = ubuntu22.04
gcc@11.4.0:
        paths:
                cc = /usr/bin/gcc
                cxx = /usr/bin/g++
                f77 = /usr/bin/gfortran
                fc = /usr/bin/gfortran
        modules  = []
        operating system  = ubuntu22.04
 

I have a branch that fixes it, once I have confirmed (by rebuilding I'd guess :( ) that it works, I'll do a PR.

[hiker]

This patch actually does not work (the script aborts), I assume the script is set to abort on error, and the grep statement fails with an error state.

Verify that it works if two consistent settings are provided (which I believe it does), e.g. I have seen:

gcc@13.2.0:
        paths:
                cc = /usr/bin/gcc
                cxx = /usr/bin/g++
                f77 = /usr/bin/gfortran
                fc = /usr/bin/gfortran
        modules  = []
        operating system  = ubuntu24.04
gcc@13.2.0:
        paths:
                cc = /usr/bin/x86_64-linux-gnu-gcc-13
                cxx = /usr/bin/x86_64-linux-gnu-g++-13
                f77 = /usr/bin/x86_64-linux-gnu-gfortran-13
                fc = /usr/bin/x86_64-linux-gnu-gfortran-13
        modules  = []
        operating system  = ubuntu24.04

[ScottWales]

Probably extracting the compiler info isn't sufficiently specific at https://github.com/MetOffice/ngmo-environments/blob/main/utils/install-compiler.sh#L40

If NGMOENVS_COMPILER is just "gcc" then you might get multiple matches, which then pass through to the other stages. Easy fix may be just to pull the first (or last, whichever spack will actually use when compiling with %gcc) matched line from the sed output.

[hiker]

While I have fixed the script (main...handle_multiple_installed_compilers) to handle incomplete compilers, the second issue still exist (no surprise) - which makes the resulting environment not working:
OMPI_FC is set to e.g. /usr/bin/gcc\n/usr/bin/x86_64-linux-gnu-gfortran-13, so mpif90 does not work. Manually fixing the environment variables results in a working environment.

[hiker]

Probably extracting the compiler info isn't sufficiently specific at https://github.com/MetOffice/ngmo-environments/blob/main/utils/install-compiler.sh#L40

If NGMOENVS_COMPILER is just "gcc" then you might get multiple matches, which then pass through to the other stages. Easy fix may be just to pull the first (or last, whichever spack will actually use when compiling with %gcc) matched line from the sed output.

That would certainly work in my case, but on my bom laptop, I have two identical compilers, so I think we need more logic there anyway :( I'll add a check that a compiler is specified with version to the sanity check ticket :)