Add the default for fontconfig cachedir #904

Job	Run time
cargo clippy (android) (armv7-linux-androideabi)	1m 11s
formatting	25s
cargo clippy (android) (aarch64-linux-android)	1m 48s
cargo check (msrv) (windows-latest)	2m 56s
cargo clippy (android) (x86_64-linux-android)	1m 48s
cargo check (msrv) (macos-latest)	46s
cargo clippy (windows-latest)	2m 19s
cargo check (msrv) (ubuntu-latest)	33s
cargo check (msrv) (android) (armv7-linux-androideabi)	31s
cargo clippy (macos-latest)	1m 35s
cargo check (msrv) (android) (aarch64-linux-android)	46s
cargo doc (windows-latest)	2m 59s
cargo clippy (ubuntu-latest)	1m 15s
cargo check (msrv) (android) (x86_64-linux-android)	46s
Prime LFS Cache	4s
cargo doc (macos-latest)	1m 9s
cargo doc (ubuntu-latest)	1m 14s
typos	4s
cargo test (windows-latest)	34s
cargo test (macos-latest)	40s
cargo test (ubuntu-latest)	32s
	23m 55s

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