watch: re-expose watch flags via execArgv #968

Job	Run time
Build slim tarball	1m 36s
aarch64-darwin: with shared libraries	27m 42s
aarch64-linux: with shared libraries	24m 22s
x86_64-linux: with shared libraries	28m 26s
x86_64-darwin: with shared libraries	59m 14s
	2h 21m 20s

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