[dsymutil] Use rfind for paths with parentheses
[dsymutil] Use rfind for paths with parentheses

Dsymutil gets library member information is through the ambiguous
/path/to/archive.a(member.o). The current logic we use would get
confused by additional parentheses. Using rfind mitigates this issue.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@355114 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit abce0e8bf5ab339e134cf8b821855e1a8bfc52a3)

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