Things you just have to know
Various things that aren't documented anywhere else.
Generally, cross-builds via qemu are only feasible for the arm and mips variants. Specifically, attempts to use powerpc64 and sparc64 under qemu simply hang.
If you use release.sh, you may use any value of WORLDDIR you wish, as long as that value is and only is /usr/src.
- release.sh also shows a misleading error message if your selected image size is too small; something like 'mdconfig: cannot open md0'.
The fix is to go into the release/<arch> subdirectory (e.g. /arm) and edit <yourboard>.conf to change IMAGE_SIZE to something larger, e.g., "3072M".
If you want to build for -CURRENT, you must build from -CURRENT. You cannot build from xyz-STABLE.
If your -CURRENT builds crash because of jemalloc, sprinkle the following magic pixie dust into /etc/make.conf:
AFAICT the armv7 src changes have not been MFCed to 11-STABLE.
Mark's TODO list