lib: make tick processor detect xcodebuild errors
node --prof-process on macOS calls out to nm(1) to look up C++
symbols. If Xcode hasn't been properly installed or its license
hasn't been accepted yet, it prints out an error and exits.
Before this commit, that error was swallowed and the output of the tick processor was not showing the C++ entry points.
This commit detects that error message and turns it into an exception. No regression test because this particular condition is hard to test for without going to extreme lengths to mock the output of nm.