Add test for quoted Env variables passed with BINDGEN_EXTRA_CLANG_ARGS. #1867

Job	Run time
msrv	3m 2s
minimal	10s
docs	17s
check-cfg	20s
quickchecking	14s
rustfmt-clippy	34s
test-book	6s
test (ubuntu-latest, 9.0, 1, 0, 0, 0, 0)	2m 4s
test-expectations (ubuntu-latest)	52s
test (ubuntu-latest, 9.0, 1, 0, 0, 1, 0)	1m 45s
test-expectations (macos-latest)	1m 50s
test (ubuntu-latest, 9.0, 1, 0, 1, 0, 0)	1m 55s
test (ubuntu-latest, 9.0, 1, 0, 1, 1, 0)	1m 53s
test (ubuntu-latest, 9.0, 1, 1, 0, 0, 0)	2m 16s
test (ubuntu-latest, 9.0, 1, 1, 0, 1, 0)	2m 12s
test (ubuntu-latest, 9.0, 1, 1, 1, 0, 0)	2m 41s
test (ubuntu-latest, 9.0, 1, 1, 1, 1, 0)	2m 16s
test (ubuntu-latest, 16.0, 1, 0, 0, 0, 0)	3m 3s
test (ubuntu-latest, 16.0, 1, 0, 0, 1, 0)	2m 40s
test (ubuntu-latest, 16.0, 1, 0, 1, 0, 0)	2m 36s
test (ubuntu-latest, 16.0, 1, 0, 1, 1, 0)	2m 34s
test (ubuntu-latest, 16.0, 1, 1, 0, 0, 0)	3m 2s
test (ubuntu-latest, 16.0, 1, 1, 0, 1, 0)	3m 2s
test (ubuntu-latest, 16.0, 1, 1, 1, 0, 0)	3m 1s
test (ubuntu-latest, 16.0, 1, 1, 1, 1, 0)	2m 59s
test (ubuntu-latest, 16.0, 0, 0, 1)	1m 48s
test (macos-latest, 9.0, 0, 0, 0)	1m 49s
	51m 1s

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