IRGen: Fix emission of reflection metadata for @objc enums

[slavapestov]

@objc enums lower as their raw type, so should go through the same
code path as imported enums.

Fixes https://bugs.swift.org/browse/SR-5625 and
rdar://problem/33683103.

[slavapestov]

@swift-ci Please smoke test

[slavapestov]

@shahmishal Looks like fallout from disabling LLDB tests in PR testing:

lit.py: /home/buildnode/disk2/workspace/swift-PR-Linux-smoke-test/branch-master/swift-integration-tests/lit.cfg:180: fatal: lldb does not exist!

[rudkx]

I just saw the same failure here: #11338

[shahmishal]

I disabled the test, however I noticed Swift(linux-x86_64).Runtime.linux-fatal-backtrace.swift has import lldb (33718631). We will need to XFail or mark it unsupported until we have lldb build fixed (33715252).

[jrose-apple]

But @objc enums should still be able to print their case names, right?

[shahmishal]

@swift-ci please clean smoke test Linux

[slavapestov]

@jrose-apple The remote reflection API does not currently have a mechanism for getting the selected case from an enum value. For now we're just using it to find references inside aggregates (with a hack for single-payload enums, like optionals... and multi-payload enums are just opaque for now).