Add a note about system dependencies for instrumentation pkgs (#2068)

Co-authored-by: Shalev Roda <[email protected]>

Author: srikanthccv

Diff for: CONTRIBUTING.md

@@ -52,9 +52,13 @@ An easier way to do so is:
 2. Run `.tox/lint/bin/isort .`
 
 See
-[`tox.ini`](https://github.com/open-telemetry/opentelemetry-python/blob/main/tox.ini)
+[`tox.ini`](https://github.com/open-telemetry/opentelemetry-python-contrib/blob/main/tox.ini)
 for more detail on available tox commands.
 
+### Troubleshooting
+
+- Some packages may require additional system wide dependencies to be installed. For example, you may need to install `libpq-dev` to run the postgresql client libraries instrumentation tests. or `libsnappy-dev` to run the prometheus exporter tests. If you encounter a build error, please check the installation instructions for the package you are trying to run tests for.
+
 ### Benchmarks
 
 Performance progression of benchmarks for packages distributed by OpenTelemetry Python can be viewed as a [graph of throughput vs commit history](https://opentelemetry-python-contrib.readthedocs.io/en/latest/performance/benchmarks.html). From the linked page, you can download a JSON file with the performance results.