Wrap `JS_FORGET_STRING_LINEARNESS` #417

Job	Run time
Integrity	15s
mac (--features debugmozjs)	12m 53s
mac	10m 12s
linux (--features debugmozjs)	7m 49s
linux	5m 21s
windows (--features debugmozjs)	16m 15s
windows (--features debugmozjs, aarch64-uwp-windows-msvc)	12m 6s
windows (--features debugmozjs, x86_64-uwp-windows-msvc)	10m 3s
windows	10m 54s
windows (aarch64-uwp-windows-msvc)	9m 35s
windows (x86_64-uwp-windows-msvc)	10m 34s
Result	1s
	1h 45m 58s

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