Fix Mac build: Add '-stdlib=libc++' #600

Job	Run time
Unit tests with default features disabled (windows-latest)	2m 24s
Unit tests with default features disabled (macos-latest)	45s
Unit tests (windows-latest, stable)	4m 5s
Unit tests with default features disabled (ubuntu-latest)	1s
Unit tests with minimum versions of direct dependencies (windows-latest)	2m 52s
Unit tests (aarch64-unknown-linux-gnu, stable)	2m 17s
Unit tests (windows-latest, 1.67.0)	2m 46s
Unit tests with minimum versions of direct dependencies (macos-latest)	5m 44s
Unit tests (aarch64-unknown-linux-gnu, 1.67.0)	5m 39s
Unit tests (macos-latest, stable)	59s
Unit tests with minimum versions of direct dependencies (ubuntu-latest)	1m 48s
Unit tests (macos-latest, 1.67.0)	4m 2s
Enforce Rust code format	12s
License / vulnerability audit (advisories)	33s
License / vulnerability audit (bans licenses sources)	22s
Clippy	54s
Unit tests (macos-13-xlarge, stable)	1m 13s
Unit tests (macos-13-xlarge, 1.67.0)	1m 30s
Unit tests (ubuntu-latest, stable)	1m 15s
Preflight docs.rs build	38s
Unit tests (ubuntu-latest, 1.67.0)	1m 10s
Preflight crate publish (ubuntu-latest, stable)	13s
Check for unused dependencies	1m 3s
ReadXMP example	1m 48s
Ensure (MAJOR) tag is used when making an API breaking change	1m 3s
	45m 16s

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