[ft] Freetype2-dev package not found when crosscompiling

[Nikolaus Neusser]

Hi @all,

i am trying to crosscompile a plugin for QT5.6, but the necessary freetype2 development package is not found by 
pkg-config.

I tried lot's of "hints" i found by google, but i am stuck.
So, i am not a crosscompiling-linux-expert, but if you could give me some hints 
i would appreciate it a lot.

my system:
  - Host: debian 8, jessie
  - target: raspberry pi 1, raspbian, jessie
  - i installed: libfreetype2-dev on the target through sudo apt-get install
  - i updated my host sysroot

Crosscompiling the plugin:
  - qmake fails with the message: "Project ERROR: freetype2 development package not 
found"
  - i export the following variables before running qmake
        sysroot=~/opt_qt_for_rpi/qt5.6.1-1/sysroot
        export PKG_CONFIG_SYSROOT_DIR=${sysroot}
        export PKG_CONFIG_DIR=
        export PKG_CONFIG_DEBUG_SPEW=1
        export 
PKG_CONFIG_LIBDIR=${sysroot}/usr/lib/pkgconfig:${sysroot}/usr/share/pkgconfig
        export PKG_CONFIG_PATH=${sysroot}
        export 
COMPILER_PATH=~/opt_qt_for_rpi/qt5.6.1-1/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian-x64/bin

This is what i tried so far:
  - searching for "ft2build.h" on the host: -> it's there
    ..sysroot/usr/include/freetype2/ft2build.h

  - letting pkg-config search for it on the host: -> it's there
      pkg-config --modversion freetype2
      -> 18.0.12

Thanks a lot,
Nik