add fix_shebang to install_step of PythonPackage easyblock so that we can fix shebangs when installing extensions

[mboisson]

…nstalling extensions

[mboisson]

The idea is being able to add something like this in an exts_list for a PythonBundle:

    ('CacheControl', '0.12.10', {
    	'fix_python_shebang_for': ['bin/doesitcache'],
    }),

or

    ('wheel', '0.37.1', {
    	'fix_python_shebang_for': ['bin/wheel'],
    }),
    ('pip', '22.0.3', {
    	'fix_python_shebang_for': ['bin/pip', 'bin/pip3'],
    }),

in order to be able to install those with multi_deps for python.

[boegel]

Test report by @boegel

Overview of tested easyconfigs (in order)

• SUCCESS tqdm-4.64.0-GCCcore-11.3.0.eb
• SUCCESS HTSeq-0.11.3-foss-2021b.eb
• SUCCESS GTDB-Tk-2.0.0-intel-2021b.eb
• SUCCESS matplotlib-3.4.2-foss-2021a.eb
• SUCCESS numexpr-2.8.1-foss-2021a.eb
• SUCCESS pybind11-2.9.2-GCCcore-11.3.0.eb

Build succeeded for 6 out of 6 (6 easyconfigs in total) node2672.swalot.os - Linux RHEL 8.4, x86_64, Intel(R) Xeon(R) CPU E5-2660 v3 @ 2.60GHz (haswell), Python 3.6.8 See https://gist.github.com/fe59b6de0274bbaacf2e805d514925a6 for a full test report.