pdl: Propagate exit code from first failure

By default, Bash will return the exit code of the last command in a
pipeline. This means that we silently ignore errors every time we pipe
the output from one command into another.

Setting the pipefail option solves this: Bash now returns the first
non-zero exit code.

Test: n/a.
Change-Id: I40cf3f246883a02167b93884df5b30824c25726f