ICU 58.x: Make sure we use the in-tree headers
ICU 58.x: Make sure we use the in-tree headers

Correct the include directories, so that we do not accidentally include
the headers that we have in the system.

fanc999/gtk-msvc-projects,fanc999/gtk-msvc-projects,fanc999/gtk-msvc-projects,fanc999/gtk-msvc-projects,fanc999/gtk-msvc-projects