Allow the library to be used from build directory

The error was:

CMake Error at C:/Libs/xtl-vs19/xtlConfig.cmake:26 (message):
  File or directory C://include referenced by variable
  xtensor_zarr_INCLUDE_DIRS does not exist !
Call Stack (most recent call first):
  C:/Libs/xtensor-zarr-vs19/xtensor-zarrConfig.cmake:49 (set_and_check)
  CMakeLists.txt:6 (find_package)

Author: dzenanz

xtensor-zarrConfig.cmake.in

@@ -21,10 +21,6 @@ find_dependency(xtensor-io @xtensor_io_REQUIRED_VERSION@)
 find_dependency(zarray @zarray_REQUIRED_VERSION@)
 find_dependency(nlohmann_json @nlohmann_json_REQUIRED_VERSION@)
 
-set(PN xtensor_zarr)
-set_and_check(${PN}_INCLUDE_DIRS "${PACKAGE_PREFIX_DIR}/@CMAKE_INSTALL_INCLUDEDIR@")
-set(${PN}_LIBRARY "")
-check_required_components(${PN})
 
 if(NOT TARGET @PROJECT_NAME@)
   include("${CMAKE_CURRENT_LIST_DIR}/@PROJECT_NAME@Targets.cmake")