This was part of "make snapshot" which does an mtree invocation before trying to populate the DESTIDR (which, for me, is "/altroot"): ===> gnu/usr.bin/gcc/libobjc install -c -o bin -g bin -m 444 NXConstStr.h /altroot/usr/include/objc/NXConstStr.h install: /altroot/usr/include/objc/NXConstStr.h: No such file or directory *** Error code 1 Stop.