bucoord: parallel make fix

bucoord: parallel make fix

Fix an instance of a Makefile rule with multiple targets.
This can cause a parallel make to fail when two instances of
compile_et compete to write the same output files.

Spotted by a build failure with a corrupt bc.h header.

Reviewed-on: http://gerrit.openafs.org/3165
Reviewed-by: Simon Wilkinson <sxw@inf.ed.ac.uk>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 0cc3cc9412c232e2ec799ee1f1a9a90f3e56ab66)
Change-Id: I453e6eced8145a0b361ce4a54baf9f7411128d2f
Reviewed-on: http://gerrit.openafs.org/3238
Tested-by: BuildBot <buildbot@rampaginggeek.com>