[yocto] How to include static library and headers in sdk

[Matt Schuckmann]

I've got a custom image and 2 custom recipes both very simple libraries that use cmake. 
I included the libraries into my image by adding 
EXTRA_IMAGEDEPENDS += "simple1"
EXTRA_IMAGEDEPENDS += "simple2" 
To my image recipe. 

When I build my image (i.e. bitbake custom-image ) I can see that the library header files and .a files are placed in the correct place in the sysroot directory. 

However when I try to create an sdk (i.e. bitbake custom-image -c populate_sdk) and then install the SDK the headers and .a files are nowhere to be found in the installed sysroot. 

What am I missing? 

Thanks,
Matt S.