No dependencies returned when one of multiple build tools fails

[benmss]

When an analysis target has multiple build tools, and one of these build tools relates to a dependency analyser that either cannot be found, or is unsupported, Macaron will report no dependencies, thereby potentially discarding legitimate results from the others.

For example, apache/flink reveals two build tools: maven and pip. As pip is not supported, the dependencies found for maven are not returned and therefore not analysed.

A solution to this problem is to continue analysis when a build tool fails, as long as there is at least one other build tool that succeeds.