This allows to figure out if a test will generate an image without
having to run it. The long term plan for this is to run the tests during
compiling ("make") and not during configuring ("cmake"). Since the list
of files to e.g. install needs to be known during configuring, this
commit is a necessary step in that direction.
Signed-off-by: Uli Schlachter <psychon@znc.in>
During build svg images of the calendar widget are generated, which
differ based on the current date.
By honouring the environment variable SOURCE_DATE_EPOCH, which is
set by distributions during build, a deterministic date can be used
at build time while keeping the normal behaviour during runtime.
See also: https://reproducible-builds.org/specs/source-date-epoch/