First notced on Raspberry Pi (Jessie/ Pixel OS - update), but seen on earlier pi Jessie too.
I had to add a couple of linker options -lX11 and -lfreetype
to get Projucer to build and run, but ONLY for the first time!
At first it wouldn’t build, then once I’d generated linux make files with the (fixed) version these options could be removed… Dunno why, but thought I’d document it in case others have have the same problem