-ffile-prefix-map option and reproducibility

[Stéphane Glondu]

Hi,

When building packages, a -ffile-prefix-map option is automatically 
injected into CFLAGS. Where does it come from? Since when?

I suspect this was added to improve reproducibility. Ironically, it 
makes packages that capture this variable non reproducible, since the 
build path seems to be randomized (has it always been the case? since 
when?). It is the case of OCaml (see #1030785), and seemingly of R as 
well (found by grepping in my /etc). I wouldn't be surprised other 
packages are affected as well.

Is there a way to not get this option? More elegant than explicitly 
filtering it out of CFLAGS in debian/rules...


Cheers,

--
Stéphane