Version 6.3.4: Fix build with Xcode. #266

Job	Run time
Windows (Win32, Ninja Multi-Config)	1h 59m 47s
Windows (x64, Ninja Multi-Config)	2h 9m 7s
Windows (x64)	2h 3m 32s
Windows (Win32)	2h 14m 50s
	8h 27m 16s

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