Fix invalid shebang for BinaryPaths script

[tdyas]

Problem

The code in https://github.com/pantsbuild/pants/blob/master/src/python/pants/engine/process.py, which uses a shell script to probe where Python interpreters are located, puts a newline in front of the shebang which can error out when remote execution environments try to execute the script. Unix/Linux requires that the shebang be the very first bytes in the file.

Solution

Strip whitespace off the front of the script. This removes the newline just after the """ marker.

Result

Remote execution in Buildbarn should pass.

[ci skip-rust]

[ci skip-build-wheels]

[Eric-Arellano]

Oh! Wow. Thank you. Travis doesn't work with this script, and I think this is likely the reason.

[coveralls]

Coverage remained the same at 0.0% when pulling 6c63a64 on tdyas:remove_newline_before_shebang into b173bcb on pantsbuild:master.

[Eric-Arellano]

Thank you!