fix: Checkout commit from forked repo #318

Job	Run time
clang++-10/canary/c++17/Debug	5m 29s
clang++-10/canary/c++17/Release	5m 25s
clang++-10/canary/c++20/Debug	4m 43s
tabtokens/clang++-10/canary/c++17/Debug	5m 40s
clang++-10/canary/c++20/Release	10m 32s
clang++-6.0/canary/c++11/Debug	5m 48s
clang++-6.0/canary/c++11/Release	7m 55s
tabtokens/clang++-10/canary/c++17/Release	5m 6s
tabtokens/clang++-10/canary/c++20/Debug	2m 48s
tabtokens/clang++-10/canary/c++20/Release	5m 49s
tabtokens/clang++-6.0/canary/c++11/Debug	2m 23s
tabtokens/clang++-6.0/canary/c++11/Release	5m 43s
clang++-10/extended/c++11/Debug	6m 32s
clang++-10/extended/c++11/Release	9m 5s
clang++-10/san/c++11/Debug	6m 1s
clang++-10/san/c++11/Debug	3m 58s
clang++-10/san/c++11/Debug	4m 33s
clang++-10/san/c++11/Debug	6m 2s
clang++-10/san/c++11/Release	4m 21s
clang++-10/san/c++11/Release	4m 10s
clang++-10/san/c++11/Release	4m 49s
clang++-10/san/c++11/Release	4m 19s
clang++-10/san/c++17/Debug	4m 7s
clang++-10/san/c++17/Debug	6m 43s
clang++-10/san/c++17/Debug	8m 2s
clang++-10/san/c++17/Debug	7m 21s
clang++-10/san/c++17/Release	7m 41s
clang++-10/san/c++17/Release	5m 39s
clang++-10/san/c++17/Release	4m 25s
clang++-10/san/c++17/Release	7m 12s
clang++-10/san/c++20/Debug	4m 36s
clang++-10/san/c++20/Debug	6m 0s
clang++-10/san/c++20/Debug	6m 54s
clang++-10/san/c++20/Debug	5m 25s
clang++-10/san/c++20/Release	4m 19s
clang++-10/san/c++20/Release	7m 11s
clang++-10/san/c++20/Release	4m 39s
clang++-10/san/c++20/Release	6m 9s
	3h 37m 34s

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