cmake:occt: add fallback

CMakeLists.txt

@@ -200,6 +200,7 @@ OPTION(FREECAD_USE_EXTERNAL_KDL "Use system installed orocos-kdl instead of the
 OPTION(FREECAD_USE_FREETYPE "Builds the features using FreeType libs" ON)
 OPTION(FREECAD_BUILD_DEBIAN "Prepare for a build of a Debian package" OFF)
 OPTION(BUILD_WITH_CONDA "Set ON if you build freecad with conda" OFF)
+OPTION(OCCT_CMAKE_FALLBACK "disable usage of occt-config files" OFF)
 if (WIN32 OR APPLE)
     OPTION(FREECAD_USE_QT_FILEDIALOG "Use Qt's file dialog instead of the native one." OFF)
 else()

cMake/FindOpenCasCade.cmake

@@ -35,7 +35,9 @@ if(OCE_FOUND)
   #set(OCC_LIBRARY_DIR ${OCE_LIBRARY_DIR})
 else(OCE_FOUND) #look for OpenCASCADE
   # we first try to find opencascade directly:
-  find_package(OpenCASCADE CONFIG QUIET)
+  if(NOT OCCT_CMAKE_FALLBACK)
+    find_package(OpenCASCADE CONFIG QUIET)
+  endif(NOT OCCT_CMAKE_FALLBACK)
   if(OpenCASCADE_FOUND)
     set(OCC_FOUND ${OpenCASCADE_FOUND})
     set(OCC_INCLUDE_DIR ${OpenCASCADE_INCLUDE_DIR})