synthesized macros source overlay fails with some specs

[reubeno]

This results in the macro file not being copied into the chroot so the load at the top of the spec fails.

Examples:
In the package autoconf, it ends up in an if:

%if "%{name}" != "autoconf"
# We're still on the autoconf-latest package
Requires: %{autoconf}
Source9999: autoconf.azl.macros
...

There are a few packages (like abattis-cantarell-fonts) where it ends up after an implicit package declaration:

%fontpkg -a

Source9999: abattis-cantarell-fonts.azl.macros

I suspect this is really a bug in the AddTag implementation.