nix-shell: support single quotes in shebangs, fix whitespace parsing (cherry picked from commit 3b99c6291377cbd22607896af9dfafa857d2f2dc) Change-Id: I2a431b21c3467eefa1ef95d5a36d672f45b6937a
I2a431b21c3467eefa1ef95d5a36d672f45b6937a