Allow skipping redirects for extensions. #403

Job	Run time
cs-stan / Coding Standard & Static Analysis	20s
testsuite / testsuite-linux (8.4, highest, false)	17s
testsuite / testsuite-linux (8.3, highest, false)	17s
testsuite / testsuite-linux (8.2, highest, false)	13s
testsuite / testsuite-linux (8.1, highest, false)	12s
testsuite / testsuite-linux (8.1, lowest, false)	15s
	1m 34s

Provide feedback