I am getting an error like this:
[WARN]Warning: Multiple build commands for output file /Developer/B/Be/build/Release-iphonesimulator/BB.app/no.png <
[WARN]Warning: Multiple build commands for output file /Developer/B/Be/build/Release-iphonesimulator/BB.app/no.png
Commenting use_frameworks! in PodFile worked for me.
#use_frameworks!
Note: Did this on XCode 10.1, pod version 1.8.4