message: fix sphinx build when PYTHONPATH is not explicitly set
diff: @@ -116,7 +116,7 @@ if (DRJIT_MASTER_PROJECT)
  set(SPHINX_OUTPUT_DIR "${CMAKE_CURRENT_BINARY_DIR}/html")
  add_custom_target(mkdoc
  - ${SPHINX_EXECUTABLE} -b html "${SPHINX_INPUT_DIR}" "${SPHINX_OUTPUT_DIR}"
  + ${CMAKE_COMMAND} -E env PYTHONPATH="${CMAKE_CURRENT_BINARY_DIR}" ${SPHINX_EXECUTABLE} -b html "${SPHINX_INPUT_DIR}" "${SPHINX_OUTPUT_DIR}"
  COMMENT "Building HTML documentation with Sphinx"
  USES_TERMINAL)
  endif()
  