Miscellanous

config.guess and config.sub are overriden only for the first three directory level
alloca can come from stdlib.h, alloca.h or not be defined at all
some system headers need explicit order e.g. sys/types.h before sys/socket.h and regex.h
C++ libraries are in compiler-specific directories, C++ creates rpath entries: don't use -lstdc++
DragonFly doesn't match *bsd*
Etoh's propolice patch still has some issues, selectively disable it on packages which produce ICE