[Buildroot] Weird behaviour of pkgconf/pkg-config

[Wolfgang Grandegger]

Hello,

I have trouble with "pkgconf", which does not find "libjpeg" when
building "qt5webengine":

  $ host/bin/pkgconf --libs libjpeg
  Package libjpeg was not found in the pkg-config search path.
  Perhaps you should add the directory containing `libjpeg.pc'
  to the PKG_CONFIG_PATH environment variable
  Package 'libjpeg', required by 'virtual:world', not found

On the other hand, "pkg-config" works as expected:

  $ host/bin/pkg-config --libs libjpeg
  -Lhost/bin/../x86_64-buildroot-linux-gnu/sysroot/usr/lib -ljpeg

At a closer look, "pkgconf" seems to search for the '*.pc" files in

  host/lib/pkgconfig/

while "pkg-config" looks into:

  host/x86_64-buildroot-linux-gnu/sysroot/usr/lib/pkgconfig/

Is that the indented behaviour? What am I doing wrong?

Wolfgang