Add oneAPI option for GCOM

[MartinDix]

NCI build configurations for GCOM 5 onwards have used

build.prop{ar}             = xiar

This is no longer included with the oneAPI compiler, https://community.intel.com/t5/Intel-Fortran-Compiler/xiar-missing-in-intel-oneapi-compiler-shared-2025-0/m-p/1646546 so we need new build configurations.

[MartinDix]

Added build configurations to a branch dev/martindix/vn8.4_nci_intel_oneapi. Rose stem build and test is ok. Also new branches for all earlier versions.

Branch 365-gcom-oneapi c0a6fae works ok in command line builds, e.g.

spack install gcom  (builds 8.4 oneAPI version)
spack install gcom@7.9 %intel

[MartinDix]

Better approach would be to create these branches in a local clone of the Met Office gcom git repo.