Python takes a lot of time to compile, ~ 25m

[jriguera]

This is because is compiled with all available optimizations.

If you do not mind compiler optimizations, just remove the flag --enable-optimizations in this section:

echo "Building and installing Python ... "
pushd Python-${PYTHON_VERSION}
  ./configure --enable-optimizations --prefix=${BOSH_INSTALL_TARGET}
  make -j 4
  make install
popd

And Python will compile in less than 5 minutes.

You can also play with the number of compilation jobs that make will spawn, usually should be based on the number of cores of a vm, normally 4 jobs is quite ok for a 2 cpus vm ...

[Rylon]

It's worth noting that without the --enable-optimizations flag, you can see a reduction in Python performance by anywhere from 10 to 20%.

For example one of the optimisations included with that flag is Profile Guided Optimisation, there are some benchmarks showing the difference here:
https://www.activestate.com/blog/2014/06/python-performance-boost-using-profile-guided-optimization

So essentially this is a trade off between optimising for build performance or optimising for execution performance.