Add the default for fontconfig cachedir #902

Job	Run time
cargo check (msrv) (windows-latest)	18s
cargo clippy (android) (armv7-linux-androideabi)	21s
cargo check (msrv) (macos-latest)	22s
cargo check (msrv) (android) (armv7-linux-androideabi)	19s
cargo clippy (android) (aarch64-linux-android)	18s
cargo clippy (windows-latest)	23s
cargo check (msrv) (ubuntu-latest)	22s
cargo check (msrv) (android) (aarch64-linux-android)	20s
cargo clippy (android) (x86_64-linux-android)	18s
cargo clippy (macos-latest)	22s
cargo check (msrv) (android) (x86_64-linux-android)	21s
cargo clippy (ubuntu-latest)	20s
cargo doc (windows-latest)	23s
formatting	29s
cargo doc (macos-latest)	18s
Prime LFS Cache	3s
typos	4s
cargo doc (ubuntu-latest)	15s
cargo test (windows-latest)	25s
cargo test (macos-latest)	24s
cargo test (ubuntu-latest)	25s
	6m 50s

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