ci: add address and undefined sanitizer tasks

The current code is clean with these two sanitizers, and we would
like to keep it that way by running the checks for any new code.

The signal of "passed with asan, but not ubsan" (or vice versa) is
not that useful in practice, so it is tempting to run both santizers
in a single task, but it seems to take forever, so tentatively let's
try having two separate ones.

Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

.github/workflows/main.yml

@@ -251,6 +251,12 @@ jobs:
           - jobname: linux-leaks
             cc: gcc
             pool: ubuntu-latest
+          - jobname: linux-asan
+            cc: gcc
+            pool: ubuntu-latest
+          - jobname: linux-ubsan
+            cc: gcc
+            pool: ubuntu-latest
     env:
       CC: ${{matrix.vector.cc}}
       CC_PACKAGE: ${{matrix.vector.cc_package}}

ci/lib.sh

@@ -278,6 +278,12 @@ linux-leaks)
 	export GIT_TEST_PASSING_SANITIZE_LEAK=true
 	export GIT_TEST_SANITIZE_LEAK_LOG=true
 	;;
+linux-asan)
+	export SANITIZE=address
+	;;
+linux-ubsan)
+	export SANITIZE=undefined
+	;;
 esac
 
 MAKEFLAGS="$MAKEFLAGS CC=${CC:-cc}"