reset vars in a couple more places #9827

Job	Run time
ormolu	7s
build ucm (ubuntu-20.04)	2m 35s
build ucm (macOS-13)	7m 49s
build ucm (windows-2019)	6m 14s
generate jit source	5s
run transcripts (ubuntu-20.04)	3m 56s
run interpreter tests (ubuntu-20.04)	1m 7s
run transcripts (macos-13)	7m 45s
run interpreter tests (macos-13)	2m 43s
run transcripts (windows-2019)	7m 44s
build jit binary / build jit binary (ubuntu-20.04)	9s
build jit binary / build jit binary (macOS-13)	20s
build jit binary / build jit binary (windows-2019)	20s
test jit / test jit (ubuntu-20.04)	7s
test jit / test jit (macOS-13)	22s
	41m 23s

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