Map the raw define value to the exported version: any non-empty string other
than the build stamp's 'unknown' placeholder passes through; everything
else (absent define, empty, placeholder) is the development fallback.
Separated from the constant so the fallback arm is testable in a build that
does inject the define.
Map the raw define value to the exported version: any non-empty string other than the build stamp's
'unknown'placeholder passes through; everything else (absent define, empty, placeholder) is the development fallback. Separated from the constant so the fallback arm is testable in a build that does inject the define.