Please check if the PR fulfills these requirements

• The PR has no duplicates (please search among thePull Requests before creating one)
• The PR followsour contributing guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

• What kind of change does this PR introduce?

(Originates from a fix for#641)
The CLIupload step searches also in fallback locations for artifacts to upload, in case these files are missing.

• What is the current behavior?

The CLIupload step assumes that the artifacts generated by the compile phase are also "exported" into the sketch folder (seethe Java IDE export feature). This means that during thecompile phase, the output files generated by the specific platform compiler are placed:

• in a temporary calculated path obtained viabuilder.GenBuildPath(sketchPath)

or

• in the user specified --build-path path
  And then "exported" (copied) into the sketch path.

This behavior could create issues for cores that do not implement correctly the "export" variables in theplatform.txt, see for examplethis core in which you have theexport recipe file extension.hex that is misaligned withthe upload file extension.zip

Since the export feature is not fundamental in the Java IDE, 3rd party core maintainers are not forced to implement it or to implement it 100% correctly, so the CLI must take in account this aspect

• What is the new behavior?

The upload command search process is the following:

1. search the User specifiedimportFile
2. search into the Sketch folder (for "exported" files)
3. search into the user specified --build-path (if passed during acompile --upload command)
4. search into temp compile folder (calculated usingbuilder.GenBuildPath(sketchPath))

• Does this PR introduce a breaking change?

Not really, this change adds fallback strategies to theupload implementation that should be transparent for the user.

• Other information:

I assumed in this PR that artifact files in fallback paths are always in this formsketch.Name+".ino"+ext and not in the exported formsketch.Name + "." + fqbnSuffix + ext

Seehow to contribute