Are you on windows? This works for me to run calibre from source not in debug mode:
Code:
set CALIBRE_DEVELOP_FROM=C:\CBH_Data\calibre.git\calibre_dev\src
set CALIBRE_CONFIG_DIRECTORY=C:\CBH_Data\calibre.git\config_test_small
start calibre
You don't need the second set if your config dir is in the standard place.