Script to compile Flang, the LLVM Fortran fornt end

Execute the scripts in this order

1. build-llvm-project.sh /path/to/flang/root
2. build-flang.sh /path/to/flang/root

Add to bin and library path

1. Add to ~/.profile
   echo "export PATH="$PATH:$HOME/installs/flang-$(date +%Y-%m-%d)/bin"" >> ~/.profile
   echo "export LD_LIBRARY_PATH="$LD_LIBRARY_PATH:$HOME/installs/flang-$(date +%Y-%m-%d)/lib"" >> ~/.profile
2. source ~/.profile