So, on Ubuntu 21 (the one I have installed), you can actually install a bazel binary from the signed repositories. Maybe earlier ubuntus too, I dunno.

# installs version 3.5.1 of the standalone bazel build tool, for me

$ sudo apt-get install bazel-bootstrap

Still, it seems incredibly rude of tensorflow to use only such a rare build tool for their project with no reasonable explanation. Bazel doesn't even support 32 bit systems. It is not hard to put all the sourcefiles into cmake or autotools, for something so widely used.

git clone https://github.com/mozilla/DeepSpeech.git

cd DeepSpeech

git checkout v0.9

git log

commit ab714a8d1b8aecc92c0a96f85e958e1a617a2f4b (HEAD -> r0.9, origin/r0.9)

Merge: 13a490d1 85d057e1

Author: lissyx <1645737+lissyx@users.noreply.github.com>

Date: Wed Apr 7 18:35:56 2021 +0200

git submodule update --init --recursive

... long time passes while the entire tensorflow history is downloaded ... I think there are flags to do it faster if needed. Could also check .gitmodules and link the module repository to another tensorflow clone, to skip it.