append defines instead of assigning
use mrbc of current build in non cross build
move debug record size assertion to correct position
Merge pull request #1597 from take-cheeze/mrbcfile

debug record size assertion fail
Fix build error for MRB_WORD_BOXING
Merge pull request #1599 from kyab/fix_mrb_word_boxing

Fix build error for MRB_WORD_BOXING