external mutator breaking on osx

working:
honggfuzz -t 3 -n 1 -e pdf -i pdf/ -Q -x -- /Applications/Adobe\ Acrobat\ Reader\ DC.app/Contents/MacOS/AdobeReader \_\_\_FILE___

breaking, adobe reader unable to process the input:
honggfuzz -c ./donothing.sh -t 3 -n 1 -e pdf -i pdf/ -Q -x -- /Applications/Adobe\ Acrobat\ Reader\ DC.app/Contents/MacOS/AdobeReader \_\_\_FILE___

donothing.sh does what it says, nothing, just simulating external modification:
#!/bin/sh
cat $1 > /tmp/bla
cat /tmp/bla > $1
rm /tmp/bla

An equally useless external mutator in c causes similar problems:
int main(){return 0;}