Is there a way to detect very sharp angles of buildings?

While not the actual heuristic you are looking for, JOSM's validator would detect a "building with almost-right angle" info-level validation error for your examples.

JOSM bug 15044 looks like wht you're looking for, but isn't implemented yet.

I am not sure how others are handling the issue but in most of the OSM maps the sharp angles (the spikes) are present. Besides the buildings the spiky configurations are present an other geometries like roads, roundabouts and so on. In almost all cases, spiky configurations are errors. Because of the maps' start scale, antialias rendering and object overlaps spikes are hardly visible and consequently they remain in the source indefinitely. At the same time, vector based GIS and map-makers should (and they do) have a tool to detect and remove spiky configurations. Actually, spikes are just special cases of tiny outgrowths created bay data generalisation while creating the scale/zoom levels (on fiords, peninsulas, tributaries and so on) and should be programmatically detected and removed. Therefor robust map-makers never see spikes in their maps.
The algorithms for the outgrowths is too complex and complicated to apply if only the spiky buildings are in focus. For this simple issue I have made a special algorithm presented in a meta language so anyone can make a program to detect and remove spikes on buildings in any languages. Besides, I have made a test and demo using OSM buildings for the UK. The algorithm, the demonstration, many examples and a visual analyses is presented/described with details here
https://drive.google.com/open?id=1MaLdnSnc454xKjn3eL95vDQKeoIW8zGU
The result and the analyses show that out of about 5625K buildings 2834 are with spiky configurations. These are detected and corrected. So, if interested, enjoy the paper in the link.