COMP: Set CTEST_GIT_UPDATE_CUSTOM and added ctest_update() to SupelElastix root test, the same way as I did for the SuperBuild.
COMP: Set CTEST_GIT_UPDATE_CUSTOM and added ctest_update() to SupelElastix root test, the same way as I did for the SuperBuild.

kaspermarstal/SuperElastix,kaspermarstal/SuperElastix,kaspermarstal/SuperElastix,SuperElastix/SuperElastix,SuperElastix/SuperElastix,SuperElastix/SuperElastix,SuperElastix/SuperElastix