After updating my POD install, Xcode sprouted a new issue:
I have no clue why the error occurred in my case, I was reusing some code from another project I created a while ago and after I adapted the code, then I always got the "Apple Mach -O Linker command failed"- Message. My best guess is, that it happened because I created/deleted some files from the project.
The thing that solved it for me was this:
Sounds stupid and I have no idea why, but it worked.