scons describes running phases itself. Running it over an empty
SConstruct yields this:
$ scons scons: Reading SConscript files ... scons: done reading SConscript files. scons: Building targets ... scons: `.' is up to date. scons: done building targets.
To suppress phase messages, add
--tree=all allows to see dependency tree for current target that
scons constructed while building.
$ scons -Q --tree=all scons: `.' is up to date. +-. +-SConstruct
. is default target, which means "build SConstruct in current directory".
SConstruct is then a dependency for building the default target.