How to systematically replace: #!/usr/bin/env python3

[Mayuresh <mayuresh%acm.org@localhost>]

When building elinks 0.18, a build time python script is having its
interpreter as:

#!/usr/bin/env python3

In a sandbox when python gets installed, the python binary has suffix
PY_VER_SUFFIX.

I tried using REPLACE_TOOL_PYTHON. But it leaves python3 untouched.

How should this be handled, so that this does not fail in bulk builds in a
sandbox?

-- 
Mayuresh