adding NSLocking back (#19) #98

Job	Run time
Build on Ubuntu (ubuntu-20.04, 5.8.1)	19s
Build on macOS (macos-13, /Applications/Xcode_14.3.1.app, 16.4, 9.4, Apple Watch Series 5 (40mm),...	10m 52s
Build on Ubuntu (ubuntu-20.04, 5.9)	36s
Build on macOS (macos-13, /Applications/Xcode_15.0.1.app, 17.0.1, 10.0, Apple Watch Series 8 (41m...	17m 6s
Build on macOS (macos-14, /Applications/Xcode_15.1.app, 17.2, 10.2, Apple Watch Series 9 (41mm), ...	8m 9s
Build on Ubuntu (ubuntu-20.04, 5.10)	20s
Build on Ubuntu (ubuntu-20.04, 6.0.1)	29s
Build on macOS (macos-14, /Applications/Xcode_15.2.app, 17.2, 10.2, Apple Watch Series 9 (45mm), ...	8m 23s
Build on Ubuntu (ubuntu-22.04, 5.8.1)	28s
Build on macOS (macos-15, /Applications/Xcode_16.1.app, 18.0, 11.0, Apple Watch Series 10 (42mm),...	2m 20s
Build on Ubuntu (ubuntu-22.04, 5.9)	37s
Build on Ubuntu (ubuntu-22.04, 5.10)	31s
Build on Ubuntu (ubuntu-22.04, 6.0.1)	24s
	50m 34s

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