CMake warning that might break things eventually

[doutriaux1]

CMake Warning (dev) at CMake/cmake_modules/pipinstaller.cmake:4 (include):
  Policy CMP0053 is not set: Simplify variable reference and escape sequence
  evaluation.  Run "cmake --help-policy CMP0053" for policy details.  Use the
  cmake_policy command to set the policy and suppress this warning.

  For input:

    '@cdat_CMAKE_BINARY_DIR@/cdat_common_environment.cmake'

  the old evaluation rules produce:

    '/Users/doutriaux1/build/CMake/cdat_common_environment.cmake'

  but the new evaluation rules produce:

    '@cdat_CMAKE_BINARY_DIR@/cdat_common_environment.cmake'

  Using the old result for compatibility since the policy is not set.
Call Stack (most recent call first):
  CMake/cdat_modules/ipython_external.cmake:6 (include)
  CMakeLists.txt:631 (include)
This warning is for project developers.  Use -Wno-dev to suppress it.