[llvm-nm] Fix use-after-free for MachOUniversalBinaries
[llvm-nm] Fix use-after-free for MachOUniversalBinaries

MachOObjectFile::getHostArch() returns a temporary, and getArchName
returns a StringRef pointing to a temporary std::string.

No tests since it doesn't trigger any errors except with the sanitizers.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@347230 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,apple/swift-llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm