parallel >= 20200822 uses /bin/echo to calculate the max allowed line
length. Patch it to a correct path, so that it doesn't (silently) fail
and fall back to a low value of 324.
Before:
$ parallel --max-line-length-allowed
324
After:
$ parallel --max-line-length-allowed
131063
Fixes: 16ca8725ff ("parallel: 20200722 -> 20200822")
