The version detection script in update.md used a space-separated string
for RUNTIME_DIRS and iterated with `for entry in $RUNTIME_DIRS`. This
relies on word-splitting which works in bash but fails in zsh (zsh does
not word-split unquoted variables by default), causing the entire string
to be treated as one entry and detection to fall through to UNKNOWN.
Fix: convert RUNTIME_DIRS and ORDERED_RUNTIME_DIRS from space-separated
strings to proper arrays, and iterate with ${array[@]} syntax which
works correctly in both bash and zsh.
Closes#1173
94b83759af