Import gcov results to SoundCloud

[jimmysoda]

Is your feature request related to a problem? Please describe.
The pdal-c build in Travis CI currently analyzes code coverage with gcov but the results are not retrieved. SoundCloud provides a way to import gcov reports.

Describe the solution you'd like
Incorporate the gcov results generated in Travis CI to SoundCloud by following the instructions in the SonarCFamily wiki page.

Describe alternatives you've considered
Set the sonar.cfamily.gcov.reportsPath value in sonar-project.properties to the location of the gcov reports. According to tests/travis/script.sh, these should be located in build/$DISTRO-$ARCH-$BUILD_TYPE, where $DISTRO can be either alpine or ubuntu and $BUILD_TYPE can be either Debug or Release. $ARCH is determined from uname -m and will likely be x86_64 for both the Alpine and Ubuntu Docker containers.

Additional context
You can use environment variables in sonar-project.properties in this form: ${env.VAR_NAME}. See SonarQube Scanner CLI issue SQSCANNER-9.

Edit - Fixed Markdown formatting