another cmake problem on osx

[Boudewijn Rempt]

With Brad's patch, I can compile again -- and it does fix
another thing, namely the endless stream of 

CMake Warning at /Users/boudewijn/src/kde/ins/share/apps/cmake/modules/KDE4Macros.cmake:570 (add_library):
  Cannot generate a safe linker search path for target xsltimport because
  files in some directories may conflict with libraries in implicit
  directories:

    link library [libxml2.dylib] in /usr/lib may be hidden by files in:
      /opt/local/lib
    link library [libz.dylib] in /usr/lib may be hidden by files in:
      /opt/local/lib
    link library [libbz2.dylib] in /usr/lib may be hidden by files in:
      /opt/local/lib

  Some of these libraries may not be found correctly.
Call Stack (most recent call first):
  filters/xsltfilter/import/CMakeLists.txt:11 (kde4_add_plugin)

messages I had before. However, now the linking path seems wrong. Most 
dependencies come from macports in my case and are located in /opt/local/lib.
This used to be no problem, but now the -L/opt/local/lib line is missing,
which gives linker errors, first in kdebase:

Linking CXX shared module ../../../lib/exrthumbnail.so
ld: library not found for -lIlmImf
collect2: ld returned 1 exit status
make[2]: *** [lib/exrthumbnail.so] Error 1

Boudewijn