Thx Sylvain,
For your fast response.
This turned out not to be the problem, since I did several times make clean & make distclean, after I created the toolchain, before posting:)
But your response helped, in that this isn't a usual problem. Therefore smt in my setup.
Turned out problem was in my CPPFLAGS include dir.
Early on, I faced a few problems with missing include files. 1 in particular <sys/_types.h> was nowhere in my system other than in Xilinx vivado,
under /gcc-arm-none-eabi/.
Once I removed it from CPPFLAGS osmocom-bb compiled fine (with a few warnings)
Problem solved:)