Audit documentation for `spicyc -c` or `spicyc -l`

[bbannier]

As of 28437292fcf01cb1602e0318924cd7c78f5429fe we might require more than the generated .cc and __linker__.cc files, see e.g., #1692. While previously it was often sufficient to call spicyc -c and spicyc -l to create all needed C++ files this can now often fail to link.

We should audit the documentation to make sure we suggest spicyc -x where possible over e.g., spicyc -c. It might even make sense to completely drop the -c and -l flags.