Clear vmthread from thread object at shutdown #18

Job	Run time
Select platforms	3s
linux-x64-hs-nopch / build (debug)	1m 56s
linux-x64-hs-minimal / build (debug)	1m 54s
docs / build (debug)	1m 55s
linux-x64 / build (debug)	1m 54s
linux-x64 / build (release)	1m 55s
linux-x64-hs-optimized / build (debug)	1m 54s
linux-x64-hs-zero / build (debug)	1m 53s
linux-x86 / build (debug)	1m 55s
linux-x86 / build (release)	1m 53s
macos-aarch64 / build (debug)	1m 48s
macos-aarch64 / build (release)	1m 39s
macos-x64 / build (debug)	1m 38s
macos-x64 / build (release)	1m 40s
windows-aarch64 / build (debug)	1m 40s
windows-x64 / build (debug)	1m 42s
windows-aarch64 / build (release)	1m 41s
windows-x64 / build (release)	1m 43s
macos-x64	1s
windows-x64	1s
linux-x64	1s
linux-cross-compile	1s
linux-x86	1s
Remove bundle artifacts	5s
	30m 53s

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