Multiple python versions (#42)

* Support multiple Python versions in single build

* RPATH + Split up config into config and runtime

* pybind11 submodule

* Docker build updates

source/docs/python.md

@@ -7,7 +7,11 @@
 ```
 
 [Omnitrace](https://github.com/AMDResearch/omnitrace) supports profiling Python code at the source-level and/or the script-level.
-Python support is enabled via the `OMNITRACE_USE_PYTHON` and `OMNITRACE_PYTHON_VERSION=<MAJOR>.<MINOR>` CMake options.
+Python support is enabled via the `OMNITRACE_USE_PYTHON` and the `OMNITRACE_PYTHON_VERSIONS="<MAJOR>.<MINOR>` CMake options.
+Alternatively, to build multiple python versions, use `OMNITRACE_PYTHON_VERSIONS="<MAJOR>.<MINOR>;[<MAJOR>.<MINOR>]"`,
+and `OMNITRACE_PYTHON_ROOT_DIRS="/path/to/version;[/path/to/version]"` instead of `OMNITRACE_PYTHON_VERSION`.
+When building multiple Python versions, the length of the `OMNITRACE_PYTHON_VERSIONS` and `OMNITRACE_PYTHON_ROOT_DIRS` lists must
+be the same size.
 
 > ***When using omnitrace for Python, the Python interpreter major and minor version (e.g. 3.7) must match the interpreter major and minor version***
 > ***used when compiling the Python bindings, i.e. when building omnitrace, a `libpyomnitrace.<IMPL>-<VERSION>-<ARCH>-<OS>-<ABI>.so` will be generated***