Let's set the stage - we have a project with a source file under a subdir of src/
.
When we compile it the first time, everything looks good - the code returns the value
defined by the macro:
$ cd /tmp
$ git clone https://github.com/erszcz/rebar_src_not_recompiled.git src_not_recompiled
$ cd src_not_recompiled
$ rg -C1 MACRO src/
src/subdir/m.erl