[GlobalISel] Simplify Select type cleanup using a ScopeExit. NFC.
[GlobalISel] Simplify Select type cleanup using a ScopeExit. NFC.

This lets us use more natural early-returns when selection fails.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@296006 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit 33f4d4644699c8071c999bdcd24e90b8af4817f3)

apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm