Package update libabseil-cpp in branch sisyphus

There exists a heap buffer overflow vulnerable in Abseil-cpp. The sized constructors, reserve(), and rehash() methods of absl::{flat,node}hash{set,map} did not impose an upper bound on their size argument. As a result, it was possible for a caller to pass a very large size that would cause an integer overflow when computing the size of the container's backing store, and a subsequent out-of-bounds memory write. Subsequent accesses to the container might also access out-of-bounds memory. We recommend upgrading past commit 5a0e2cb5e3958dd90bb8569a2766622cb74d90c1