Tracked within Apple by <rdar://problem/36754225> Swift CI:
parse_stdlib.sil tests failing with vtable verification. The error is
an assertion failure that we haven't traced back to its cause yet:
Assertion failed: (EntriesSZ == VTableEntryCache.size() && "Cache
size is not equal to true number of VTable entries"), function
verify, file /Users/buildnode/jenkins/workspace/
oss-swift-package-osx/swift/lib/SIL/SILVerifier.cpp, line 4747.
The sharding of this test buys us nothing, because it was only sharding
the AST verifier, which is an insignificant portion of the runtime
(and memory usage) of this test. Given that the test takes ~2m30s to run
and consumes > 2GB memory, having 17 copies of it running is a problem.
