build.py --platform js success check may be faulty

[dan-rigdon-bel]

I recently failed to build the javascript library using:

python scripts/build.py --platform js -o -v

because there was a build error. However, the script reported success (and the error was suppressed). I suspect the check for success is looking for a file and it is finding an older build and reporting success when it should not. This can be tested by artificially introducing a build error in the code.

[mcneel-build]

Linked with RH3DM-100

[fraguada]

Recent testing confirms that the appropriate files are removed with the -o flag

[fraguada]

I've noticed that this is an issue on dotnet builds. build.py declares success, but there are errors reported.