ObjectLibraryAssembler duplicate detection is case-sensitive, fails on NTFS

[roman-bcny]

ddbb57d added duplicate basename detection to ObjectLibraryAssembler, but the detection uses exact (case-sensitive) string comparison on basenames. On NTFS and default macOS APFS (both case-insensitive), files like Repeat.o and repeat.o pass the duplicate check but collide on disk. The copy fails with Win32Error(code: 80) / NSCocoaErrorDomain Code=516.

Reproduces with swift build (swiftbuild backend) on swift-argument-parser on Windows. The Examples/repeat/ target produces both Repeat.o (from Repeat.swift) and repeat.o (module emit for module repeat). Same issue on color, math, default-as-flag examples.

[roman-bcny]

cc @daveinglis

[jakepetroules]

Hmm, we'll probably need to add some suffix/disambiguator.

[roman-bcny]

The suffix was already added by the change I linked:

swift-build/Sources/SWBTaskExecution/TaskActions/ObjectLibraryAssemblerTaskAction.swift

Line 55 in 070cdf8

// Duplicate detected, add suffix before extension

                    // Duplicate detected, add suffix before extension
                    let nameWithoutSuffix = input.withoutSuffix
                    let suffix = input.fileSuffix  // Includes the dot
                    destinationName = "\(Path(nameWithoutSuffix).basename)-\(count)\(suffix)"

The files are named {base}-1.o, {base}-2.o etc - when collision is detected. The issue is that collision is not detected because "Repeat" != "repeat" but paths are still colliding on disk.

ps. forgot to cc @compnerd :)