SizeofXXTypeInBits and additional library needed and other things

[sonicsmooth]

Typo in nlvm/llgen.nim line 1171

sizeOfXTypeInBits(dl, ty).uint32

should be

sizeOfXXTypeInBits(dl, ty).uint32

Also, I found on my system sudo apt install libzstd-dev is needed. Maybe that can go in the intructions.

Also for building llvm, in make-llvm.sh, I found the following options useful. I'm not sure how universal this is:
cmake -GNinja -DLLVM_USE_LINKER=lld -DCMAKE_C_COMPILER=gcc -DCMAKE_CXX_COMPILER=g++ -DLLVM_ENABLE_LLD=OFF "$@" ..

thanks