RFR: 8308290: Add fontconfig requirement to building.md

[Erik Joelsson]

On Wed, 17 May 2023 14:41:01 GMT, Jan Kratochvil <duke at openjdk.org> wrote:

> After following all the commands in `building.md` I still get on Fedora 38 x86_64:
> 
> 
> checking for fontconfig/fontconfig.h... no
> configure: error: Could not find fontconfig!
> 
> 
> Another issue is that it is all written with `yum` instead of `dnf` but people can handle it I guess.

Marked as reviewed by erikj (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/14034#pullrequestreview-1431053997