tree e80443566cb8fc154053b235952cf25313f6dbdb
parent b9760aba9380eb9032e72deddf76df0050a54de9
author Jake Petroules <jake.petroules@apple.com> 1522188571 -0700
committer Jake Petroules <jake.petroules@petroules.com> 1522200687 -0700

Prevent spurious rebuilds with SwiftPM builds of llbuild

The generate-version-h.sh script was writing a new version.h file (thus
updating the timestamp, thus triggering a change detection by the build
system) every time it was run, regardless of whether the content had
actually changed. Only update the file if doing so will actually change
the content, in order to make null builds actually work again.