git: openjdk/jdk: 8308290: Add fontconfig requirement to building.md

[Yuri Nesterenko]

Changeset: 57b8ed13
Author:    Jan Kratochvil <jan at jankratochvil.net>
Committer: Yuri Nesterenko <yan at openjdk.org>
Date:      2023-05-18 08:48:16 +0000
URL:       https://git.openjdk.org/jdk/commit/57b8ed13984eab1ab0eaf70c1904dc0f50fe6129

8308290: Add fontconfig requirement to building.md

Reviewed-by: erikj

! doc/building.html
! doc/building.md