PCL on archlinux, VTK cmake error

When I compiled PCL on archlinux, I got this error
"
CMake Error at //lib/vtk-5.10/VTKTargets-debug.cmake:1281 (MESSAGE):
The imported target "vtkWrapTcl" references the file

"//bin/vtkWrapTcl"

but this file does not exist. Possible reasons include:

* The file was deleted, renamed, or moved to another location.

* An install or uninstall procedure did not complete successfully.

* The installation package was faulty and contained

"//lib/vtk-5.10/VTKTargets-debug.cmake"

but not all the files it references.
"

Some other AUR packages have similar problems, such as this, ginkgo-cadx.

I figured out cmake variable VTK_DIR is somehow undefined. I don't know it is a bug of cmake or vtk on arch. I found a workaround, export VTK_DIR=/where/is/vtk before calling cmake.