Link error for messaging tests when configure was run without "-tests" option

The tests like:
tests/auto/qmessage
depends on Qt Mobility symbols only present when configure was run with "-tests" option. Ideally is possible to automatically skip the compilation of tests/auto/qmessage when -tests option was not used.

Test case 1(example for *nix):

• confirm that the following compilation test passes

  ./configure -modules 
  make && make install
  cd tests/auto
  qmake
  make
  

Test case 2(example for *nix):

• confirm that the following compilation test passes

  ./configure -modules multimedia -tests
  make