[Ubuntu & Fedora] INSTALL lib compilation error

[mathildemerle]

On Ubuntu and Fedora, the dev branch fails to compile due to bad paths:

Install the project...
-- Install configuration: "Release"
-- Installing: /lib/libmedCore.so
CMake Error at layers/medCore/cmake_install.cmake:52 (file):
  file INSTALL cannot copy file
  "/mnt/storage/workspace/med-ubuntu-weekly/build/medInria-build/lib/libmedCore.so"
  to "/lib/libmedCore.so": Permission denied.
Call Stack (most recent call first):
  layers/cmake_install.cmake:47 (include)
  cmake_install.cmake:47 (include)

The "/lib/libmedCore.so" seems wrong