adding NSLocking back #99

Job	Run time
Build on macOS (macos-13, /Applications/Xcode_14.3.1.app, 16.4, 9.4, Apple Watch Series 5 (40mm),...	1s
Build on Ubuntu (ubuntu-20.04, 5.8.1)	17s
Build on macOS (macos-13, /Applications/Xcode_15.0.1.app, 17.0.1, 10.0, Apple Watch Series 8 (41m...	1s
Build on Ubuntu (ubuntu-20.04, 5.9)	28s
Build on macOS (macos-14, /Applications/Xcode_15.1.app, 17.2, 10.2, Apple Watch Series 9 (41mm), ...	1s
Build on Ubuntu (ubuntu-20.04, 5.10)	32s
Build on macOS (macos-14, /Applications/Xcode_15.2.app, 17.2, 10.2, Apple Watch Series 9 (45mm), ...	1s
Build on Ubuntu (ubuntu-20.04, 6.0.1)	30s
Build on macOS (macos-15, /Applications/Xcode_16.1.app, 18.0, 11.0, Apple Watch Series 10 (42mm),...	1s
Build on Ubuntu (ubuntu-22.04, 5.8.1)	22s
Build on Ubuntu (ubuntu-22.04, 5.9)	22s
Build on Ubuntu (ubuntu-22.04, 5.10)	23s
Build on Ubuntu (ubuntu-22.04, 6.0.1)	25s
	3m 24s

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