watch: re-expose watch flags via execArgv #3449

Job	Run time
Build slim tarball	2m 29s
aarch64-linux: with shared libraries	29m 7s
aarch64-darwin: with shared libraries	31m 3s
x86_64-linux: with shared libraries	35m 49s
x86_64-darwin: with shared libraries	3h 19m 55s
	4h 58m 23s

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