`Too many levels of recursion in macro expansion` error when calling `Specfile.update_version()`

[nforro]

Trivial reproducer:

# recursive macro definition
%global cflags "-O3 %{cflags}"

Name:           test
Version:        0.1
Release:        %autorelease
Summary:        Test package

License:        MIT

%description
Test package

%changelog
%autochangelog

spec = Specfile("test.spec")
spec.update_version("0.2")

This raises specfile.exceptions.RPMException: Too many levels of recursion in macro expansion. It is likely caused by recursive macro declaration..

A workaround is to define the macro (even to an empty value):

spec = Specfile("test.spec", macros=[("cflags", "")])
spec.update_version("0.2")