Revert "Search in default path before calling pkg-config"
Build system changes can be potentially breaking and so must be reviewed
prior to commit. In addition, there is no explanation for this change.
Simon, you might want to submit your patches to Phabricator for review
prior to landing them.
CCMAIL: sdepiets@gmail.com
This reverts commit 4f4f3295f2a8a366c954025652785e8fda34df3e.