Issue with compatibility with X11R6 (Quartz) libs

[Caius Aérobus]

Hello,
I downloaded and compiled Qt under Mac OsX 10.9.4, everything worked fine.
Then I installed X11R6 (Quartz project for Mac) because I need libGLU.
And now I can no longer run qmake:

qt-everywhere-opensource-src-4.8.6 $ qmake
dyld: Symbol not found: __cg_png_create_info_struct
  Referenced from: /System/Library/Frameworks/ImageIO.framework/Versions/A/ImageIO
  Expected in: /usr/X11R6/lib/libPng.dylib
 in /System/Library/Frameworks/ImageIO.framework/Versions/A/ImageIO
Trace/BPT trap: 5
qt-everywhere-opensource-src-4.8.6 $

qt-everywhere-opensource-src-4.8.6 $ qmake
dyld: Symbol not found: __cg_png_create_info_struct
  Referenced from: /System/Library/Frameworks/ImageIO.framework/Versions/A/ImageIO
  Expected in: /usr/X11R6/lib/libPng.dylib
 in /System/Library/Frameworks/ImageIO.framework/Versions/A/ImageIO
Trace/BPT trap: 5
qt-everywhere-opensource-src-4.8.6 $

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First I suspected that Qt was first compiled with its own version of a couple of libraries, such as libPng, and there is now an incompatibility issue with those of X11R6.
So I rebuilt Qt so that it uses X11 libs, but still the same issue.
Any help?