CI Speedup

[varunagrawal]

Specialize Boost install so that the CI is faster.

This gives a ~17 minute improvement since Boost install goes down from ~22 mins to ~5 mins.

Shoutout to @ProfFan for making me aware of this!

[varunagrawal]

Added some further performance improvements. This gives a 4x improvement on Linux, and 2x on macOS. Windows is still problematic (Release version takes 2 hours both before and after!), but we removed the dependency on the MarkusJx Boost action which is nice.
Some CI workflows have increased in time, but the increase is very tolerable (e.g. 18m to 21m) especially considering the gains we've made.

CI Job	Previous Runtime	New Runtime
Linux CI / ubuntu-18.04-gcc-5 Debug (push)	63m	14m
Linux CI / ubuntu-18.04-gcc-5 Release (push)	50m	13m
Linux CI / ubuntu-18.04-gcc-9 Debug (push)	69m	15m
Linux CI / ubuntu-18.04-gcc-9 Release (push)	62m	15m
Linux CI / ubuntu-18.04-clang-9 Debug (push)	50m	11m
Linux CI / ubuntu-18.04-clang-9 Release (push)	61m	14m
Special Cases CI / ubuntu-gcc-tbb Debug	62m	17m
Special Cases CI / ubuntu-gcc-tbb Release	64m	15m
Special Cases CI / ubuntu-cayleymap Debug	60m	16m
Special Cases CI / ubuntu-cayleymap Release	60m	14m
Special Cases CI / ubuntu-gcc-deprecated Debug	58m	14m
Special Cases CI / ubuntu-gcc-deprecated Release	61m	15m
Special Cases CI / ubuntu-gcc-quaternions Debug	66m	16m
Special Cases CI / ubuntu-gcc-quaternions Release	48m	16m
Python CI / ubuntu-18.04-gcc-5 Debug Python 3	22m	21m
Python CI / ubuntu-18.04-gcc-5 Release Python 3	16m	21m
Python CI / ubuntu-18.04-gcc-9 Debug Python 3	21m	22m
Python CI / ubuntu-18.04-gcc-9 Release Python 3	19m	21m
Python CI / ubuntu-18.04-clang-9 Debug Python 3	14m	11m
Python CI / ubuntu-18.04-clang-9 Release Python 3	17m	18m
Python CI / macOS-10.15-xcode-11.3.1 Debug Python 3	14m	19m
Python CI / macOS-10.15-xcode-11.3.1 Release Python 3	20m	23m
Python CI / ubuntu-18.04-gcc-5-tbb Debug Python 3	22m	18m
Python CI / ubuntu-18.04-gcc-5-tbb Release Python 3	20m	15m
Windows CI / windows-2019-cl Debug	14m	20m
Windows CI / windows-2019-cl Release	165m	176m
Linux CI / ubuntu-18.04-gcc-5 Debug	65m	13m
Linux CI / ubuntu-18.04-gcc-5 Release	56m	15m
Linux CI / ubuntu-18.04-gcc-9 Debug	64m	18m
Linux CI / ubuntu-18.04-gcc-9 Release	54m	11m
Linux CI / ubuntu-18.04-clang-9 Debug	45m	13m
Linux CI / ubuntu-18.04-clang-9 Release	49m	11m
macOS CI / macOS-10.15-xcode-11.3.1 Debug	30m	14m
macOS CI / macOS-10.15-xcode-11.3.1 Release	34m	14m

[dellaert]

This is awesome! What was the biggest timesaver on Linux?

[varunagrawal]

For Linux, not installing all of Boost and using make -j$(nproc) gave the biggest savings. For Mac, I did the same trick for make but with the appropriate command to figure out number of cores on the system.