[CMake] make clean and install prefix

[Tomasz Grobelny]

I have a project which contains one subdirectory and one external project
contained in another subdirectory (this is to use different compiler for
the "external" project). I don't have administrative privileges on the
system, so I need to perform installation to a different directory. I add
-DCMAKE_INSTALL_PREFIX=/path/to/install/dir/ to cmake invocation, then type
"make install" and everything is fine (files correctly installed to my
location). But if I do "make clean" and then "make install" once again then
it seems that cmake forgets about my installation directory and tries to
install to /usr/local/ (which of course fails because of lack of filesystem
permissions). I found a workaround: if I delete external_project-prefix
directory after "make clean" and then do "make install" then everything is
working fine again. What can I do not to have to remove this directory
every time?
I'm using cmake 2.8.4.
-- 
Regards,
Tomasz Grobelny