see if we can support modifying the PYTHONPATH env var from cmake.

[llnl]

see if we can support modifying the PYTHONPATH env var from cmake.

[cyrush]

in future versions of cmake we may be able to use cmake -E env

add_custom_command(OUTPUT  ${CMAKE_CURRENT_BINARY_DIR}/build
        COMMAND ${CMAKE_COMMAND} -E env PYTHONPATH=${CMAKE_BINARY_DIR}/${dest_dir} 
        ${PYTHON_EXECUTABLE} ${setup_file} -v
        build
        --build-base=${CMAKE_CURRENT_BINARY_DIR}/build
        install
        --install-purelib=${CMAKE_BINARY_DIR}/${dest_dir}
        DEPENDS  ${setup_file} ${ARGN}
        WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR})

[cyrush]

Will setting CMake Python Module dir help?

[cyrush]

on linux and osx, we can use shell syntax to set the python path env var,

for example instead of
${PYTHON_EXECUTABLE} ${setup_file} -v

use:
PYTHONPATH=${CMAKE_BINARY_DIR}/${dest_dir} ${PYTHON_EXECUTABLE} ${setup_file} -v

it's not clear if this helps us on windows

[cyrush]

closing this, it's a build time message -- and has never lead to a real issue.

We expect to build in our own location, we can recast this as just a friendly reminder we are doing so.