Compiling OSG 2.8.0 in Cygwin- missing -lGL and -lGLU during linker stage

Otherwise there will be a lot of error output like this:

[ 15%] Building CXX object src/osg/CMakeFiles/osg.dir/Viewport.o
Linking CXX shared library ../../bin/cygosg-2.8.0.dll
CMakeFiles/osg.dir/AlphaFunc.o:AlphaFunc.cpp:(.text+0x14): undefined
reference to `_glAlphaFunc'
CMakeFiles/osg.dir/BlendColor.o:BlendColor.cpp:(.text+0x159):
undefined reference to `_glGetString'
CMakeFiles/osg.dir/BlendColor.o:BlendColor.cpp:(.text+0x288):
undefined reference to `_glGetString'
CMakeFiles/osg.dir/BlendColor.o:BlendColor.cpp:(.text+0x3c8):
undefined reference to `_glGetString'
CMakeFiles/osg.dir/BlendColor.o:BlendColor.cpp:(.text+0x1263):
undefined reference to `_glGetString'
CMakeFiles/osg.dir/BlendEquation.o:BlendEquation.cpp:(.text+0x1b9):
undefined reference to `_glGetString'