It's impossible to conditionally use a crate based only on cargo features, so
temporarily disable the backend on all Windows builds while we sort out how
to get the UWP builds working again.
Various UWP GStreamer improvements
There are a number of positive changes in these commits:
* we successfully load GStreamer plugins in ARM64 UWP builds
* we correctly link the ARM64 ANGLE libraries when appropriate
* it is no longer necessary to manually set the LIB environment variable on Windows
* we automatically download and link against UWP-friendly GStreamer binaries when building with `--uwp`
* the use of vcruntime140.dll, msvcp140.dll and api-ms-win-crt-runtime-l1-1-0.dll in the UWP application has been removed and the build does not repackage them
* the set of base supporting GStreamer DLLs has been expanded to allow the gstlibav plugin to load correctly
---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `___` with appropriate data: -->
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix#23742
- [x] There are tests for these changes
<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/23863)
<!-- Reviewable:end -->
[hololens] More events, remove most of the statics, better shutdown
Depends on #23831
- Buttons are greyed out when necessary
- Reload, Stop, Back and Fwd are properly bound
- Servo.cpp rewritten in a much cleaner way
- Removed most of the statics
- Improved (but not full) shutdown
<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/23845)
<!-- Reviewable:end -->
Make Windows arm64 easy
* Add a ServoApp project configuration
* Add a `--win-arm64` build flag (now `python mach build -r --win-arm64 --uwp`)
* Automatically set up GStreamer LIB environment
* Yell if the cross-compilation environment isn't set up correctly
* Automatically find the Visual C++ installation for DLL packaging, rather than relying on an environment variable
---
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix#23793 and fix#23795
- [x] There are tests for these changes
<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/23841)
<!-- Reviewable:end -->
