Disable cmake warning due to PCL 1.11.1.

This is a temporary workaround.
See here: PointCloudLibrary/pcl#3680
When this PCL issue is fixed, the changes done in this commit should be removed.

CMake Warning (dev) at /usr/local/Cellar/cmake/3.18.4/share/cmake/Modules/FindPackageHandleStandardArgs.cmake:273 (message):
  The package name passed to `find_package_handle_standard_args` (libusb-1.0)
  does not match the name of the calling package (PCL).  This can lead to
  problems in calling code that expects `find_package` result variables
  (e.g., `_FOUND`) to follow a certain pattern.
Call Stack (most recent call first):
  /usr/local/share/pcl-1.11/PCLConfig.cmake:290 (find_package_handle_standard_args)
  /usr/local/share/pcl-1.11/PCLConfig.cmake:337 (find_libusb)
  /usr/local/share/pcl-1.11/PCLConfig.cmake:549 (find_external_library)
  cmake/VISPUtils.cmake:536 (find_package)
  CMakeLists.txt:593 (VP_OPTION)
This warning is for project developers.  Use -Wno-dev to suppress it.

CMakeLists.txt

@@ -133,6 +133,16 @@ set(VISP_VERSION "${VISP_VERSION_MAJOR}.${VISP_VERSION_MINOR}.${VISP_VERSION_PAT
 # Package revision number
 set(VISP_REVISION "1")
 
+#-----------------------------------------------------------------------------
+# TO BE CHECKED BEFORE NEXT RELEASE
+#
+# see here: https://github.com/PointCloudLibrary/pcl/issues/3680
+# when this is fixed, we can remove the following 3 lines.
+if(NOT DEFINED CMAKE_SUPPRESS_DEVELOPER_WARNINGS)
+  set(CMAKE_SUPPRESS_DEVELOPER_WARNINGS 1 CACHE INTERNAL "No dev warnings")
+endif()
+#-----------------------------------------------------------------------------
+
 find_file(GNU_INSTALL_DIRS_FROM_CMAKE NAMES GNUInstallDirs.cmake PATHS ${CMAKE_ROOT}/Modules)
 mark_as_advanced(GNU_INSTALL_DIRS_FROM_CMAKE)
 if(GNU_INSTALL_DIRS_FROM_CMAKE)