Unset LIBRARY_PATH before builds

See https://gcc.gnu.org/onlinedocs/gcc/Environment-Variables.html

Closes Homebrew/homebrew-versions#592.
youtube-dl 2014.12.17.2

Closes #35056.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>
youtube-dl: update 2014.12.17.2 bottle.
Merge remote-tracking branch 'upstream/master'