Roll buildroot to e522d38d629d7522f0589e754886ed2b82232d9e

[cbracken]

Contains:

• Dynamically link against system fontconfig (Dynamically link against system fontconfig buildroot#701)

Migrates from a statically-linked fontconfig to dyanmically linked. This is likely to fix various fontconfig-related issues such as:

• Slow first-frame startup performance on desktop Linux flutter#118911
• Failures seen in [Linux][a11y] implement AtkText::get_text/string_at_offset() #38144

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read and followed the Flutter Style Guide and the C++, Objective-C, Java style guides.
• I listed at least one issue that this PR fixes in the description above.
• I added new tests to check the change I am making or feature I am adding, or Hixie said the PR is test-exempt. See testing the engine for instructions on writing and running engine tests.
• I updated/added relevant documentation (doc comments with ///).
• I signed the CLA.
• All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel on Discord.

[cbracken]

Closing -- I originally opened this as a backup in case @vially wasn't around to update/land #40725 given how long it was pending, but that patch is good to go now. I've pushed the roll commit to that PR.