09ac6c81be
11736dbe3dbe34bcb430d05810b9e9aa66ec1cd6 build, qt: Hardcode last modified timestamp in Qt RCC (Hennadii Stepanov)
Pull request description:
Our Guix build system sets the [`SOURCE_DATE_EPOCH`](https://reproducible-builds.org/specs/source-date-epoch/) and propagates it to the depends build subsystem. Its [default value](https://github.com/bitcoin/bitcoin/blob/master/contrib/guix/README.md#recognized-environment-variables) is the top commit timestamp.
After bumping Qt version up to 5.15.2, due to [this](1ffcca4cc2) change, every time they are going to make new Guix builds for another branch/commit they must ensure that the `qt` package will be rebuilt from scratch. Otherwise, Bitcoin Core GUI binaries will be non-deterministic.
Such behavior makes working with Guix builds suboptimal.
This PR fixes the described issue by patching Qt RCC and hardcoding last modified timestamps with `1`.
It's worth to mention that this change is compatible with a possible future [improvement](https://github.com/bitcoin/bitcoin/pull/21995) which makes each dependency package reproducible.
A drawback of such an approach is not currently applied to our project, as it effectively makes [QML cache files](https://bugreports.qt.io/browse/QTBUG-57182) useless. I can't say it's a problem for the https://github.com/bitcoin-core/gui-qml project.
---
**A note for thinkers:** For now this change is enough as only Qt source contains `SOURCE_DATE_EPOCH`. But in general we should re-think about treating the `SOURCE_DATE_EPOCH` variable in the depends build subsystem. For instance, its default value could be the output of `git log --format=%at -1 -- depends`.
ACKs for top commit:
fanquake:
ACK 11736dbe3dbe34bcb430d05810b9e9aa66ec1cd6
Tree-SHA512: 31f104010a0a78d217aafcc5bc4606351f9060fc2a827277935b85fc8ced9f3d90a31d812c7db8c2711fb6daccd279cf0945dc1d7a7199e0eb0ade451cdbcd5d
Bitcoin Core integration/staging tree
For an immediately usable, binary version of the Bitcoin Core software, see https://bitcoincore.org/en/download/.
Further information about Bitcoin Core is available in the doc folder.
What is Bitcoin?
Bitcoin is an experimental digital currency that enables instant payments to anyone, anywhere in the world. Bitcoin uses peer-to-peer technology to operate with no central authority: managing transactions and issuing money are carried out collectively by the network. Bitcoin Core is the name of open source software which enables the use of this currency.
For more information read the original Bitcoin whitepaper.
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