Add a quick build mode for fast development builds

[yfyf]

Triggered by the very slow live ISO builds while testing the remote control on the PlayOS PC.

Switching to lz4 compression makes building of installer and live ISOs 2-4x faster.

squashfs compression is a low-level aspect that can only affect booting, but is otherwise irrelevant for dev builds. This makes the iteration loop much quicker.

Benchmarks:

Live

~364% faster with lz4

Quick

time QUICK_BUILD=1 nix-build --arg buildVm false --arg buildInstaller false --arg buildBundle false \
    --arg buildLive true --arg buildDisk false --arg versionOverride '"2025.3.1-live-quick1"'

building '/nix/store/xy8m3mds8yaxsr43qlxrbbh97hwf8vsf-playos-2025.3.1-live-quick1.drv'...
/nix/store/al4f3pdzwxsx64gkv9g7cwaq3pcnx1fn-playos-2025.3.1-live-quick1

real    1m23.322s
user    0m11.132s
sys     0m0.585s

Regular

time nix-build --arg buildVm false --arg buildInstaller false --arg buildBundle false \ 
    --arg buildLive true --arg buildDisk false --arg versionOverride '"2025.3.1-live-slow1"'


building '/nix/store/12apqrwn1ij8nky4ygikpi06ljdilcwv-playos-2025.3.1-live-slow1.drv'...
/nix/store/f1vry1hxnbwi4ra9vfh4k36sgjwg29w4-playos-2025.3.1-live-slow1

real    5m20.110s
user    0m11.151s
sys     0m0.635s

Installer

~251% faster with lz4

Quick

time QUICK_BUILD=1 nix-build --arg buildVm false --arg buildInstaller true --arg buildBundle false \
    --arg buildLive false --arg buildDisk false --arg versionOverride '"2025.3.1-installer-quick1"'


building '/nix/store/jbv09mbdmhnm9zk7yvlzfxh2irb3fr4d-playos-2025.3.1-installer-quick1.drv'...
/nix/store/wp6x3wfq2f2g2pw8jpw25knhif668p0n-playos-2025.3.1-installer-quick1

real    2m20.440s
user    0m14.893s
sys     0m0.695s

Regular

time nix-build --arg buildVm false --arg buildInstaller true --arg buildBundle false \
    --arg buildLive false --arg buildDisk false --arg versionOverride '"2025.3.1-installerslow1"' --show-trace


building '/nix/store/633zh44a80x2c77g1y5s1k339crycf72-playos-2025.3.1-installerslow1.drv'...
/nix/store/1kbg3fnzngacan7c5z8qiyzsjcayw451-playos-2025.3.1-installerslow1

real    5m51.535s
user    0m15.066s
sys     0m0.790s

Checklist

• Changelog updated
• Code documented
• User manual updated

[knuton]

Nice!

Two small suggestions

[knuton]

Should we do something like fail if quickBuild is set, but updateUrl is not the dummy default value?

[yfyf]

Hmm, I would say no, it is useful in situations where you want to test updates? The only thing I would do is to consider the "official" targets like ./build validation or ./build master to abort if QUICK_BUILD is set.

[knuton]

Also fine

[yfyf]

Implemented the restriction in a79134e

[yfyf]

There are really strange E2E test failure due to... this:

  playos # [   14.217674] xsession[1473]: Traceback (most recent call last):
  playos # [   14.220751] xsession[1473]:   File "/nix/store/z42d2zkscmgy9qlfffv3iigvvw41x6hr-playos_kiosk_browser-0.1.0/bin/...kiosk-browser-wrapped-wrapped-wrapped", line 7, in <module>
  playos # [   14.228387] xsession[1473]:     import kiosk_browser
  playos # [   14.231277] xsession[1473]:   File "/nix/store/z42d2zkscmgy9qlfffv3iigvvw41x6hr-playos_kiosk_browser-0.1.0/lib/python3.12/site-packages/kiosk_browser/__init__.py", line 9, in <module>
  playos # [   14.237687] xsession[1473]:     from kiosk_browser import main_widget
  playos # [   14.240862] xsession[1473]:   File "/nix/store/z42d2zkscmgy9qlfffv3iigvvw41x6hr-playos_kiosk_browser-0.1.0/lib/python3.12/site-packages/kiosk_browser/main_widget.py", line 9, in <module>
  playos # [   14.247240] xsession[1473]:     from kiosk_browser import browser_widget, captive_portal, dialogable_widget, proxy as proxy_module
  playos # [   14.251825] xsession[1473]:   File "/nix/store/z42d2zkscmgy9qlfffv3iigvvw41x6hr-playos_kiosk_browser-0.1.0/lib/python3.12/site-packages/kiosk_browser/browser_widget.py", line 1, in <module>
  playos # [   14.259305] xsession[1473]:     from PyQt6 import QtCore, QtWidgets, QtWebEngineWidgets, QtWebEngineCore, QtGui, QtSvgWidgets
  playos # [   14.265379] xsession[1473]: ImportError: libQt6WebEngineWidgets.so.6: cannot open shared object file: No such file or directory

Edit: the container runs out of memory while installing:

2025-10-15T11:40:24.1065363Z tar: Removing leading `/' from member names
2025-10-15T11:40:24.1113516Z tar: Removing leading `/' from hard link targets
2025-10-15T11:41:14.8917469Z tar: /nix/store/iwzz3by31rh9gy0vjknwg196w44icmba-qtwebengine-6.8.1/lib/: Cannot savedir: Cannot allocate memory
2025-10-15T11:42:28.2538953Z tar: 3.16GiB 0:02:04 [26.0MiB/s] [                       <=>                        ]Exiting with failure status due to previous errors
2025-10-15T11:42:28.2539384Z 
2025-10-15T11:42:28.8328453Z '/nix/store/kgixlj6bi484fvrkca8z13am94sxhkxw-nixos-system-playos-playos-2025.3.1-TEST/kernel' -> '/mnt/system/kernel'
2025-10-15T11:42:28.8459052Z '/nix/store/kgixlj6bi484fvrkca8z13am94sxhkxw-nixos-system-playos-playos-2025.3.1-TEST/initrd' -> '/mnt/system/initrd'
2025-10-15T11:42:28.8607061Z '/nix/store/kgixlj6bi484fvrkca8z13am94sxhkxw-nixos-system-playos-playos-2025.3.1-TEST/init' -> '/mnt/system/init'
2025-10-15T11:42:29.2276804Z mke2fs 1.47.1 (20-May-2024)

The strange thing is that it still continues despite the error. Will look into it.

[knuton]

Is this reviewable or in need of further work?

[yfyf]

Is this reviewable or in need of further work?

It is reviewable, I believe the E2E test failure was unrelated and due to the CI VM running out of memory.