Turning off whole-module optimization not (fully) supported?

[dabrahams]

My project is blocked by an apparent whole-module optimization buh. I am unable to work around it by turning off whole-module optimization because swift-llbuild complains of a missing dependencies file.

Reproducer:

• swift package init --type executable
• add swiftSettings: [.unsafeFlags(["-no-whole-module-optimization"])] to the executable target
• swift build -c release

This problem could be worked around in the compiler, in swift-llbuild, or in the driver by separately issuing the build command without -no-whole-module-optimization included, which generates the needed dependencies file. I am filing issues against all three projects in the hopes that the maintainers can agree on a possible solution.

• swift issue