enhance tbb easyblock by adding option to build Python bindings

[zarybnicky]

(created using eb --new-pr)

TBB bundles a number of language bindings in the same source tree, also including make targets to build them. This PR add an extra_option with_python that enables building the Python bindings. For this to be used, Python and SWIG must be in the dependency list (SWIG as a builddependency), as well as a Makefile patch - these are provided in the easyconfig.

Given that the next version of TBB is implemented as a mix of CMake+Bazel (instead of Make+CMake used by TBB v.2020.3, which this PR is for), it seems that the entire easyblock will need to be rebuilt in the next update anyway.

[boegel]

Test report by @boegel

Overview of tested easyconfigs (in order)

• SUCCESS tbb-2019_U4-GCCcore-8.2.0.eb
• SUCCESS tbb-2020.1-GCCcore-9.3.0.eb
• SUCCESS tbb-2020.3-GCCcore-10.2.0.eb

Build succeeded for 3 out of 3 (3 easyconfigs in total)
node2620.swalot.os - Linux centos linux 7.9.2009, x86_64, Intel(R) Xeon(R) CPU E5-2660 v3 @ 2.60GHz (haswell), Python 3.6.8
See https://gist.github.com/b23d2fc561b423c21ef47cc9f8f3567f for a full test report.

[zarybnicky]

@boegel Wait a minute, I messed up PYTHONPATH

I first used set_environment to set it, which worked for sanity checks but not for epiScanPy bundle (because I was overwriting the variable, duh) - and now that I've changed it to prepend_paths, the epiScanPy sanity checks don't pass...

I'll need to take a closer look tomorrow

[zarybnicky]

...duh once again 🙈 I saw a bunch of GitHub notifications and remembered I have a WIP in my terminal, nevermind :)

[boegel]

Going in, thanks @zarybnicky!