ci: exercise unsafe OpenSSL backend

In the preceding commit we have fixed a segfault when using an unsafe
SHA1 backend that is different from the safe one. This segfault only
went by unnoticed because we never set up an unsafe backend in our CI
systems. Fix this ommission by setting `OPENSSL_SHA1_UNSAFE` in our
TEST-vars job.

Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: pks-t

ci/run-build-and-tests.sh

@@ -17,6 +17,7 @@ linux-gcc)
 	export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
 	;;
 linux-TEST-vars)
+	export OPENSSL_SHA1_UNSAFE=YesPlease
 	export GIT_TEST_SPLIT_INDEX=yes
 	export GIT_TEST_MERGE_ALGORITHM=recursive
 	export GIT_TEST_FULL_IN_PACK_ARRAY=true