Fix setup instructions for Arch
base-devel contains the last version of autoconf. However, some
dependencies of the project rely on autoconf 2.13. Without this change,
the build fails with the following message:
```
ERROR: Could not find autoconf 2.13
--- stderr
ERROR: Could not find autoconf 2.13
make: *** [makefile.cargo:143: maybe-configure] Error 1
thread 'main' panicked at 'assertion failed: result.success()', build.rs:110:5
note: Run with `RUST_BACKTRACE=1` for a backtrace.
```
<!-- Please describe your changes on the following line: -->
---
<!-- 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
- [ ] These changes fix #__ (github issue number if applicable).
<!-- Either: -->
- [ ] There are tests for these changes OR
- [x] These changes do not require tests because they just change documentation on how to build.
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base-devel contains the last version of autoconf. However, some
dependencies of the project rely on autoconf 2.13. Without this change,
the build fails with the following message:
```
ERROR: Could not find autoconf 2.13
--- stderr
ERROR: Could not find autoconf 2.13
make: *** [makefile.cargo:143: maybe-configure] Error 1
thread 'main' panicked at 'assertion failed: result.success()', build.rs:110:5
note: Run with `RUST_BACKTRACE=1` for a backtrace.
```
Format components canvas and canvas_traits #21373
<!-- Please describe your changes on the following line: -->
```bash
rustfmt components/canvas/**/*.rs
rustfmt components/canvas_traits/**/*.rs
```
<!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.-->
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<!-- 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/21538)
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Update pkg-config to avoid setting LIBPATH to point to gstreamer deps…
… on Windows
I haven't tested locally, but AppVeyor will tell us if this works.
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Update x11-dl to pickup the fix for x11 startup crash
This updates x11-dl to 2.18.3 to get https://github.com/erlepereira/x11-rs/issues/90
<!-- Please describe your changes on the following line: -->
---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [ ] `./mach build -d` does not report any errors
- [ ] `./mach test-tidy` does not report any errors
- [X] These changes fix#21530 (github issue number if applicable).
<!-- Either: -->
- [ ] There are tests for these changes OR
- [X] These changes do not require tests because it's fixing a startup crash
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<!-- 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/21532)
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