Need official way to use pkg-config, regardless of what Qt's setting was

I am trying to build my application on the 5.8.0 441 snapshot for MacOS/Android/iOS to check QTBUG-51131, but I believe something has changed in how pkg-config is handled by clang+qmake.

The way:
macx:QT_CONFIG -= no-pkg-config
CONFIG += link_pkgconfig
PKGCONFIG += sndfile

has been working on every 5.x release, but not on 5.8.0. The error I've got is:
Project WARNING: pkg-config disabled, can't check package existence
Project ERROR: sndfile development package not found

Doing just PKGCONFIG += sndfile seems to go a bit further but then the sndfile headers cannot be found at build time.