Merge pull request #4 from gabm/master

Problem: cppfs cannot be installed to non-system directories in system-dir-install

CMakeLists.txt

@@ -68,6 +68,7 @@ option(OPTION_SELF_CONTAINED "Create a self-contained install with all dependenc
 option(OPTION_BUILD_TESTS    "Build tests."                                           ON)
 option(OPTION_BUILD_DOCS     "Build documentation."                                   OFF)
 option(OPTION_BUILD_EXAMPLES "Build examples."                                        OFF)
+option(OPTION_FORCE_SYSTEM_DIR_INSTALL "Force system dir install"                     OFF)
 
 
 # 
@@ -119,7 +120,7 @@ if("${CMAKE_INSTALL_PREFIX}" STREQUAL "/usr" OR "${CMAKE_INSTALL_PREFIX}" STREQU
 endif()
 
 # Installation paths
-if(UNIX AND SYSTEM_DIR_INSTALL)
+if((UNIX AND SYSTEM_DIR_INSTALL) OR OPTION_FORCE_SYSTEM_DIR_INSTALL)
     # Install into the system (/usr/bin or /usr/local/bin)
     set(INSTALL_ROOT      "share/${project}")       # /usr/[local]/share/<project>
     set(INSTALL_CMAKE     "share/${project}/cmake") # /usr/[local]/share/<project>/cmake