PSA: Linux & Android non-lto builds now linking with mold

[Andrew Grieve]

• It's been enabled for is_android for a couple of weeks.
• I've just now enabled it for is_linux
• It makes link steps go faster, especially for machines with a lot of cores
• 3-4x on Google workstations
• It's rolled out only for the main repro (build_with_chromium)
• but can be disabled via `use_mold=false` GN arg.

There are some extra details in https://crbug.com/40208899.