version 8.11 fails to download

[davekaro]

Heroku build reports:

-----> Building libvips binary...
       Downloading libvips 8.11.0 source archive
       Unpacking libvips source archive
tar: This does not look like a tar archive
gzip: stdin: not in gzip format

The automated version detector returns 8.11.0 today (see https://github.com/Verumex/heroku-buildpack-libvips/blob/master/bin/buildscript.sh#L47-L55) which sets a version and download URL like:

https://github.com/libvips/libvips/releases/download/v8.11.0/vips-8.11.0.tar.gz

see https://github.com/Verumex/heroku-buildpack-libvips/blob/master/bin/buildscript.sh#L80

However, the actual download URL for version 8.11 is:

https://github.com/libvips/libvips/releases/download/v8.11/vips-8.11.0.tar.gz

Note the missing minor number. This might be a mistake of the libvips release process, or a change. I have not thought of the best way to fix yet, just wanted to share my findings so far.