Add support for compiling with Intel oneAPI DPC++/C++ compiler

[Civil]

Currently in WAF it is hardcoded that gcc needs to be available, so you can't just do:

source /opt/intel/oneapi/setvars.sh intel64
export CC="icx"
export CXX="icpx"
./b configure && ./b build

As it will fail with:

Could not find gcc/g++ (only Clang), if renamed try eg: CC=gcc48 CXX=g++48 waf configure

That should be a warning instead to allow people to experiment with different compilers.

There are few minor fixes required for it to compile with icx 2024.0, I can submit those if you are interested.

P.S. Also based on my initial tests, if compiled with icx it performs about 10% better (and performance is more stable) on Xeon W5-3435X (Sapphire Rapids WS-112L), compared to gcc 12.