[Cmake] ADD_CUSTOM_COMMAND and PRE_BUILD

[Benjamin Rutt]

I'm using cmake 1.8.3.  I read that ADD_CUSTOM_COMMAND can be used in
the following way, quoted from 'cmake --help ADD_CUSTOM_COMMAND':

       The second signature adds a custom command to a target such as a
       library or executable.  This is useful for performing an operation
       before or after building the target:

         ADD_CUSTOM_COMMAND(TARGET target
                            PRE_BUILD | PRE_LINK | POST_BUILD
                            COMMAND command
                            [ARGS [args...]]
                            [COMMENT comment])

       This defines a new command that will be associated with building the
       specified target.  When the command will happen is determined by which
       of the following is specified:

         PRE_BUILD - run before all other dependencies
         PRE_LINK - run after other dependencies
         POST_BUILD - run after the target has been built

So I'd like to use the PRE_BUILD to get my custom command to run
before any of the dependencies for the named target are built.
Here's my sample project:

    ::::::::::::::
    CMakeLists.txt
    ::::::::::::::
    PROJECT(dummyproj)

    ADD_LIBRARY(dummylib SHARED foo.cpp)

    ADD_CUSTOM_COMMAND(
      TARGET dummylib
      PRE_BUILD
      COMMAND cp
      ARGS -v /etc/hosts ${dummyproj_BINARY_DIR})

    ::::::::::::::
    foo.cpp
    ::::::::::::::
    class Foo
    {
        int a;
        int b;
    };

So I'd like the 'cp' command to execute before any dependencies of
dummylib are built.  Yet the output shows that the 'cp' command is
happening after foo.o and libdummylib.so are built.  I'd like the 'cp'
command to happen before both of them are built.  What am I doing
wrong?

    $ cmake ../dummyproj 
    -- Check for working C compiler: gcc
    -- Check for working C compiler: gcc -- works
    -- Check for working CXX compiler: g++
    -- Check for working CXX compiler: g++ -- works
    -- Configuring done
    -- Generating done
    $ make
    Building dependencies. cmake.depends...
    cmake.depends is up-to-date
    Building object file foo.o...
    Building shared library libdummylib.so...
    `/etc/hosts' -> `/home/rutt/dev/dummyproj/build/hosts'

Thanks,
-- 
Benjamin