This merges work done by yorickvP and timokau in #63208 and #63616 respectively.
Now the derivation builds both libtensorflow and the Python package and puts them into
different outputs.
Quite a bit of improvements were done on the top, including:
* Use official tag revision as source, not a branch;
* Use all system libraries possible (before only one was actually used);
* Move various environment variables to the derivation itself from hooks;
* Use source Python build instead of wheel build to ensure fixup hooks do their important jobs on libraries;
* And more that I forgot!
Turns out markers are non-deterministic after all and even our patching still
doesn't solve this problem completely. For example (tensorflow deps, this is a
complete diff so actual dependencies don't differ):
30509c30509
< bc527ff00916b15caee38793bca8f294c748df4a256de55c5199281be0489e73 result/@bazel_skylib.marker
---
> 4e0303e815c78df1e43d4b88dfe65e73046e0c6157fb10aa9a4e8b910113cd9c result/@bazel_skylib.marker
31045c31045
< fa13d04b2316214c3b4008b52546c2d5b633e006f6f019d597bb3f9745bacf7b result/@bazel_toolchains.marker
---
> b36174bf5535e5157801b6de30c35ee03a03fe57766306393c3d65dd65cbebf4 result/@bazel_toolchains.marker
31144c31144
< b0ce4a3ac29ac22528336dd3a54b5b7af9ecc43bef2a2630713c1981a5cbbb51 result/@build_bazel_rules_swift.marker
---
> 7492528068ec4f8e7ace2ecf8f933ec4e1b2235bd7426ce6f70177919f1cd05e result/@build_bazel_rules_swift.marker
36245c36245
< be2993536a8233d63251b664caf35b1e7cd57d194ab2a39a293876c232d6bbd0 result/@io_bazel_rules_closure.marker
---
> b6655cc3f2c78525e5a724d8a4e93b1e7f09f1e09fc817d231109e7f39103e88 result/@io_bazel_rules_closure.marker
36329c36329
< 087bc674c9509dfe157400d111db4a13eeb45fc76aeccd490cee9aad6771ecad result/@io_bazel_rules_docker.marker
---
> f920ec07315ec71e800b05cd22b2a341c0a80807c6e335ee81739b13c532b422 result/@io_bazel_rules_docker.marker
79544d79543
< 85893a05a817036c61f6cd9f8247757baa1654f473c494ce4fc5253c2bbd2790 result/@platforms.marker
And here's an example of differences:
$ cat result-a/@bazel_skylib.marker
7dc7472d37424ba5ec6a5532765bc911
$MANAGED
cat result-b/@bazel_skylib.marker
a8f3f577798201157128e8e9934c4705
$MANAGED
Instead of trying to patch these markers further we now completely clear them.
Nix hacks for ignoring markers are restored and expanded so that we don't even
attempt to parse the marker.
See #64258 for more details and some discussion.
Fix#22729.
tl;dr: This fixes the behaviour at run-time but uses "n/a" defaults
inside the Nix build sandbox (build-time).
There might still be a few minor regressions, we might have to tweak
the behaviour over time (e.g. the implementation from Debian also
differs from the original version), and we could refactor the script,
but it should work well enough for now.
