servo: Merge #16389 - Allow bootstrapping on Debian (from aneeshusa:support-debian-for-mach-bootstrap); r=jdm

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This is needed for servo/saltfs#631, since the Travis builders are detected as `'debian'` for some reason.

---
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- [ ] `./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).

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- [ ] There are tests for these changes OR
- [x] These changes do not require tests because the test will be in saltfs

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Source-Repo: https://github.com/servo/servo
Source-Revision: 2e82d98afff696dfd574087a0806383a6abc4c78

--HG--
extra : subtree_source : https%3A//hg.mozilla.org/projects/converted-servo-linear
extra : subtree_revision : 86333237f56fdbd41bfb84a1605efb3fee06b215

servo/python/servo/bootstrap.py

@@ -270,7 +270,13 @@ def bootstrap(context, force=False):
         bootstrapper = windows_msvc
     elif "linux-gnu" in host_triple():
         distro, version, _ = platform.linux_distribution()
-        if distro in ['CentOS', 'CentOS Linux', 'Fedora', 'Ubuntu']:
+        if distro.lower() in [
+            'centos',
+            'centos linux',
+            'debian',
+            'fedora',
+            'ubuntu',
+        ]:
             context.distro = distro
             bootstrapper = salt