Make scripts fail fast

[fzyzcjy]

When using it (incorrectly), I got something like

mv: rename ./_target/deps/mathlib/src/all.lean to ./_target/deps/minif2f/lean/src/all.lean: No such file or directory
./scripts/setup.sh: line 15: ./_target/deps/minif2f/lean/src/all.lean: No such file or directory
./scripts/setup.sh: line 16: ./_target/deps/minif2f/lean/src/all.lean: No such file or directory

However, the script continues running and thus it is easy for users not to realize this problem. Thus, to follow the best practices of shell scripting, I add the flags to make it fail fast.