Hello gentooers!

Maybe some of you can help me with this one. I'm trying to create an ebuild to 
test some of our university software on my laptop. It is using cmake as a 
build tool. CMakeLists.txt states the following (among others :)

SET(PREFIX ${CMAKE_INSTALL_PREFIX})
SET(INCLUDEDIR_B "${PREFIX}/include")

INSTALL(CODE "FILE(MAKE_DIRECTORY ${INCLUDEDIR_B}/iwPlugins)")

Everything is compiling fine, but the install procedure gets interrupted with a 
sandbox violation:

ACCESS DENIED  mkdir:        /usr/include/iwPlugins                                                                                                                                 
CMake Error at cmake_install.cmake:92 (FILE):                                                                                                                                       
  file problem creating directory: /usr/include/iwPlugins                                                                                                                           


It seems for me that the variable INCLUDEDIR_B is not expanded to the sandbox 
path but /usr/include within the CODE statement. Other INSTALL instructions 
like FILES and TARGETS work fine. Is it advisable to have another method of 
creating an empty directory?

Thanks in advance
Patrick