Strange messages from gems after switching to Xcode 6 and Yosemite

Question

I recently switched to Xcode 6 and Yosemite. Now, when I run certain gems I get the following messages. I've seen other questions on here with the same error message, but none of them seem to match this.

Is this due to a known change in the dev environment? Do I need to reinstall all my gems?

$ mygem start
Ignoring bigdecimal-1.2.5 because its extensions are not built.  Try: gem pristine bigdecimal-1.2.5
Ignoring debase-0.0.9 because its extensions are not built.  Try: gem pristine debase-0.0.9
Ignoring ffi-1.9.3 because its extensions are not built.  Try: gem pristine ffi-1.9.3
Ignoring redcarpet-3.1.1 because its extensions are not built.  Try: gem pristine redcarpet-3.1.1
Ignoring xcodeproj-0.17.0 because its extensions are not built.  Try: gem pristine xcodeproj-0.17.0
Ignoring bigdecimal-1.2.5 because its extensions are not built.  Try: gem pristine bigdecimal-1.2.5
Ignoring debase-0.0.9 because its extensions are not built.  Try: gem pristine debase-0.0.9
Ignoring ffi-1.9.3 because its extensions are not built.  Try: gem pristine ffi-1.9.3
Ignoring redcarpet-3.1.1 because its extensions are not built.  Try: gem pristine redcarpet-3.1.1
Ignoring xcodeproj-0.17.0 because its extensions are not built.  Try: gem pristine xcodeproj-0.17.0

Answer 1

for each gem that is being ignored you will have to run:

gem install %gemname%

and then

gem pristine %gemname%