Consider using sysroot or sysroot scripts inside Docker

[Eloston]

Chromium's sysroot scripts have quite a few modifications to maximize compatibility of their builds (see HacksAndPatchesCommon in https://chromium.googlesource.com/chromium/src.git/+/master/build/linux/sysroot_scripts/sysroot-creator.sh). We should include them so we have the same compatibility as official Chrome/Chromium.

There are two ways we could implement this:

1. Modify the Docker environment with these hacks. We may have to reimplement the hacks ourselves in this case.
2. Add another build method that creates a sysroot image and configure GN to use it. It should be possible to add this to build.sh, but I don't know how easy that is. It also makes the Docker container a bit redundant.

[Eloston]

Discussion welcome on choosing a solution (or finding another one).

[clickot]

the sysroot feature is used in the meantime