Only output on nix verbose builds and only output to stderr

[arrowmaster]

Prevent any output on non verbose nix builds and only output to stderr on verbose builds to avoid introducing unexpected output from non unity processes that UnityDoorstop gets injected into.

The behavior can be observed in 4.4.0 and 4.4.1 with the following test case.

$ DOORSTOP_ENABLED=1 LD_PRELOAD=./libdoorstop.so cat <(echo "This should be the only output")
Failed to hook dlsym, ignoring it. Error: no such function: dlsym
Failed to hook dup2, ignoring it. Error: no such function: dup2
This should be the only output

[ManlyMarco]

Looks good to me. The newlines are still added, right?

[arrowmaster]

Looks good to me. The newlines are still added, right?

Yes the newlines are added by the LOG function so they were removed in the lines that were changed from printf to LOG.

The output shown in #88 is actually from this build. It didn't solve the problem I was trying to solve but its still a necessary step and got me further in troubleshooting.