This is what I found when debugging Cmake problems when building kdebase.

[castro@castro2 kdebase]$ grep -r "WITH_XCOMPOSITE" *
CMakeLists.txt:option( WITH_XCOMPOSITE "Enable xcomposite support" OFF )

**** kicker/taskmanager compiles OK with or without XCOMPOSITE.

kicker/taskmanager/CMakeLists.txt:if( WITH_XCOMPOSITE )
kicker/taskmanager/CMakeLists.txt:endif( WITH_XCOMPOSITE )

**** kwin/kompmgr does not compile with or without XCOMPOSITE.

Looking into kompmgr.c shows that it requires XCOMPOSITE
#include <X11/extensions/Xcomposite.h>
#include <X11/extensions/Xdamage.h>
#include <X11/extensions/Xrender.h>
#include <X11/extensions/shape.h>

     The question is should we have the option (WITH_XCOMPOSITE) in 
kompmgr/CMakeLists.txt.

kwin/kompmgr/CMakeLists.txt:if( WITH_XCOMPOSITE )
kwin/kompmgr/CMakeLists.txt:endif( WITH_XCOMPOSITE )

If the answer is YES then should try and build it?

Looking into kwin/kompmgr/configure.in.in

if test "x$with_composite" != "xno"; then
KDE_CHECK_HEADERS(X11/extensions/Xdamage.h,,compile_kompmgr=no,[#include 
<X11/Xlib.h>])
KDE_CHECK_HEADERS(X11/extensions/Xcomposite.h,,compile_kompmgr=no,[#include 
<X11/Xlib.h>])
KDE_CHECK_HEADERS(X11/extensions/Xrender.h,,compile_kompmgr=no,[#include 
<X11/Xlib.h>])
else
     compile_kompmgr=no
fi

it shows us that we should NOT build it.

kwin/CMakeLists.txt:    if( WITH_XCOMPOSITE )
                                                 add_subdirectory( kompmgr )
kwin/CMakeLists.txt:    endif( WITH_XCOMPOSITE )

[castro@castro2 kdebase]$

The changes I have made to kwin/kompmgr/CMakeLists.txt are quick & dirty,
but it works for now.

I will put some more thought to it in the next few days.

Castro.