MacOS: replaced version specific paths with /usr/local/opt paths

CMakeLists.txt

@@ -31,10 +31,10 @@ elseif(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
 endif()
 
 if(APPLE)
-  link_directories(/usr/local/lib /usr/local/opt/gettext/lib /usr/local/Cellar/libsigc++@2/2.10.2/lib)
+  link_directories(/usr/local/lib /usr/local/opt/gettext/lib /usr/local/opt/libsigc++@2/lib)
   include_directories(/usr/local/opt/gettext/include)
   set(CMAKE_MACOSX_RPATH 1)
-  set(ENV{PKG_CONFIG_PATH} "$ENV{PKG_CONFIG_PATH}:/usr/local/lib/pkgconfig:/opt/X11/lib/pkgconfig:/usr/local/Cellar/libffi/3.2.1/lib/pkgconfig:/usr/local/Cellar/libsigc++@2/2.10.2/lib/pkgconfig")
+  set(ENV{PKG_CONFIG_PATH} "$ENV{PKG_CONFIG_PATH}:/usr/local/lib/pkgconfig:/opt/X11/lib/pkgconfig:/usr/local/opt/libffi/lib/pkgconfig:/usr/local/opt/libsigc++@2/lib/pkgconfig")
 endif()
 if(${CMAKE_SYSTEM_NAME} MATCHES FreeBSD)
   link_directories(/usr/local/lib)