Qt 5: revert 5.9.2; remove build temporary directory

[ttuegel]

Motivation

This PR groups two unrelated changes to Qt 5.9 to reduce rebuilds.

Qt 5.9.2 breaks all Kirigami applications. KDE has requested that we revert one commit (which breaks SDDM) or downgrade to Qt 5.9.1.

It is no longer necessary to create a temporary symlink farm when building Qt 5 packages. This should make it easier to use nix-shell to develop Qt projects.

Testing

• Tested using sandboxing (nix.useSandbox on NixOS, or option build-use-sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.

---

[orivej]

It is no longer necessary to create a temporary symlink farm when building Qt 5 packages.

This is very welcome! Am I reading it right that you've accomplished this primarily with fixQtModulePaths and fixQtBuiltinPaths?

[ttuegel]

Most of the work is just to set QMAKEPATH correctly. fixQtModulePaths and fixQtBuiltinPaths are to clean up other developers' faulty assumptions. Qt developers tend to assume that all of Qt is installed to the same prefix as qmake (false) and that it is safe to install new components in the same prefix as qmake (also false).

[orivej]

Thank you!

I've noticed that somehow cmd = $$system("type -p $$2") in defineTest(qtHaveModule) in qtbase.patch is impure, it executes type in /bin/sh on NixOS and Linux, and this fails on Linux when /bin/sh is dash because its type prints

$ type -p ls
-p: not found
ls is /bin/ls

and then qmake attemps to execute -p: not found uic is /nix/store/.... command -v prints just the path in both bash and dash, but maybe we could find a pure solution?

[bjornfor]

Replacing "type -p" with "command -v" makes it POSIX sh compatible, and thus it should work in dash.

[dtzWill]

@ttuegel looks like fe0ab94 (:+1: for the refactoring cleanup!) is incomplete for 5.6:

• The old directories and files are still present, but at first glance appear unused.
• At least one of the patches for 5.6 didn't make it into the corresponding uber-patch, namely for ICU 59, without which it currently doesn't build (cc mendeley: 1.17.10 -> 1.17.11 #31443).

Thanks for wrangling all this!

[ttuegel]

Replacing "type -p" with "command -v" makes it POSIX sh compatible, and thus it should work in dash.

Thanks for the tip!

At least one of the patches for 5.6 didn't make it into the corresponding uber-patch, namely for ICU 59, without which it currently doesn't build (cc #31443).

Ugh, this must have gone fubar when I merged master in; it certainly was building when I tested.

[orivej]

Previously enableParallelBuilding defaulted to true. Why have you change it to false?

[lukeadams]

Note: this does break qt5 on darwin.
Changes so far to get it to build:

• erroneous -inotify configure flag
• erroneous -gtk configure flag
• this patch