Expand NVCC documentation

[ptheywood]

From discussions on the Bede slack, the following additions to the nvcc documentation may be useful:

• [x] Using --forward-unknown-to-host-compiler to forward unknown compiler args from nvcc to g++/clang (i.e. -march=native) + the linker version.
• [x] Using --compiler-optinos / -Xcompiler etc to explicitly provide arguments to separate compilation phases (i.e. -march=native)
• [x] Using --compiler-bindir / -ccbin to set the host compiler to something other than the first gcc/g++ on the path.
  • [x] Explain what the host compiler will be by default, + specify certain combinations may be blocked by nvcc without a specific flag.
• [x] -lineinfo for improved profiling on optimised builds
• [x] -G for device debug (mutually exclusive with -lineinfo on recent nvcc)