Comment 5 for bug 1920825

If we only want to replace environment variables and nothing else, we can use

#!/usr/share/dh-exec/dh-exec-subst-env

then even with DEB_BUILD_PROFILES set, the lines preserve the leading whitespace.

It would be nice for DEB_BUILD_PROFILES to preserve leading whitespace and/or only strip it for files where it matters and not others. I guess .symbols is one of the few special ones where leading whitespace is required.