[Qt] Refactor and clean up the qmake build system
The qmake build system has accumulated a bit of cruft and redundancy
over time. There's also a fairly tight coupling between how to build
the various targets, and _what_ to build, making it harder to add new
rules or sources. This patch aims to elevate these issues somewhat.
This is a short-list of the changes:
- The rules for how to build targets are now mostly contained as
prf-files in Tools/qmake/mkspecs/features. Using mkspecs also
allows us to do pre- and post-processing of each project file,
which helps to clean up the actual project files.
- Derived sources are no longer generated as a separate make-step
but is part of each target's project file as a subdir. Makefile
rules are used to ensure that we run make on the derived sources
before running qmake on the actual target makefile. This makes
it easier to keep a proper dependency between derived sources
and the target.
- We use GNU make and the compiler to generate dependencies on
UNIX-based systems running Qt 5. This allows us to lessen the
need to run qmake, which should reduce compile time.
- WebKit2 is now build by default if building with Qt 5. It can
be disabled by passing --no-webkit2 to build-webkit.
The result of these changes are hopefully a cleaner and easier
build system to modify, and faster build times due to no longer
running qmake on every single build. It's also a first step
towards possibly generating the list of sources using another
build system.
https://bugs.webkit.org/show_bug.cgi?id=71222
Reviewed by Simon Hausmann.
