emerging newtonsoft-json failed because mono renamed their master branch

[Hati-]

While trying to emerge dev-dotnet/buildtools I got this error:

 * newtonsoft-json-6.0.8.zip SHA256 SHA512 WHIRLPOOL size ;-) ...                                                                                                                             [ ok ]
>>> Downloading 'https://github.com/mono/mono/raw/master/mcs/class/mono.snk'
--2021-05-18 16:23:00--  https://github.com/mono/mono/raw/master/mcs/class/mono.snk
Resolving github.com... 140.82.121.4
Connecting to github.com|140.82.121.4|:443... connected.
HTTP request sent, awaiting response... 404 Not Found
2021-05-18 16:23:00 ERROR 404: Not Found.

!!! Couldn't download 'mono.snk'. Aborting.
 * Fetch failed for 'dev-dotnet/newtonsoft-json-6.0.8-r1', Log file:
 *  '/var/tmp/portage/dev-dotnet/newtonsoft-json-6.0.8-r1/temp/build.log'

>>> Failed to emerge dev-dotnet/newtonsoft-json-6.0.8-r1, Log file:
[...]

Seems like the mono repo renamed their default master branch to main, and since github doesn't redirect .../raw/... URLs to the new branch it fails with a 404 File Not Found.