Search for a better openvdb find module if available

Solves prusa3d#6681, alternative path for openvdb installation can be specified via cache variable

CMakeLists.txt

@@ -33,6 +33,8 @@ option(SLIC3R_MSVC_PDB          "Generate PDB files on MSVC in Release mode" 1)
 option(SLIC3R_PERL_XS           "Compile XS Perl module and enable Perl unit and integration tests" 0)
 option(SLIC3R_ASAN              "Enable ASan on Clang and GCC" 0)
 
+set(OPENVDB_FIND_MODULE_PATH "" CACHE PATH "Path to OpenVDB installation's find modules.")
+
 set(SLIC3R_GTK "2" CACHE STRING "GTK version to use with wxWidgets on Linux")
 
 set(IS_CROSS_COMPILE FALSE)
@@ -492,13 +494,17 @@ find_package(NLopt 1.4 REQUIRED)
 if(SLIC3R_STATIC)
     set(OPENVDB_USE_STATIC_LIBS ON)
     set(USE_BLOSC TRUE)
-endif()
+endif ()
 
-find_package(OpenVDB 5.0 REQUIRED COMPONENTS openvdb)
+find_package(OpenVDB 5.0 COMPONENTS openvdb)
 if(OpenVDB_FOUND)
     slic3r_remap_configs(IlmBase::Half RelWithDebInfo Release)
     slic3r_remap_configs(Blosc::blosc RelWithDebInfo Release)
-endif()
+else ()
+    message(FATAL_ERROR "OpenVDB could not be found with the bundled find module. "
+                   "You can try to specify the find module location of your "
+                   "OpenVDB installation with the OPENVDB_FIND_MODULE_PATH cache variable.")
+endif ()
 
 set(TOP_LEVEL_PROJECT_DIR ${PROJECT_SOURCE_DIR})
 function(prusaslicer_copy_dlls target)

cmake/modules/FindOpenVDB.cmake

@@ -102,6 +102,27 @@ may be provided to tell this module where to look.
 
 #]=======================================================================]
 
+# If an explicit openvdb module path was specified, that will be used
+if (OPENVDB_FIND_MODULE_PATH)
+  set(_module_path_bak ${CMAKE_MODULE_PATH})
+  set(CMAKE_MODULE_PATH ${OPENVDB_FIND_MODULE_PATH})
+  find_package(
+    OpenVDB ${OpenVDB_FIND_VERSION} QUIET
+    COMPONENTS
+      ${OpenVDB_FIND_COMPONENTS}
+  )
+
+  set(CMAKE_MODULE_PATH ${_module_path_bak})
+  if (OpenVDB_FOUND)
+    return()
+  endif ()
+
+  if (NOT OpenVDB_FIND_QUIETLY)
+    message(STATUS "Using bundled find module for OpenVDB")
+  endif ()
+endif ()
+# ###########################################################################
+
 cmake_minimum_required(VERSION 3.3)
 # Monitoring <PackageName>_ROOT variables
 if(POLICY CMP0074)