a. error message:
ERROR: Multiple .bb files are due to be built which each provide libgcc (/home/<username>/workspace/os2/meta-sourcery/recipes/meta/external-sourcery-toolchain.bb /home/<username>/workspace/os2/poky/meta/recipes-devtools/gcc/libgcc_4.9.bb).
 This usually means one provides something the other doesn't and should.


b. bitbake -e | grep ^PREFERRED_PROVIDER.*libgcc
PREFERRED_PROVIDER_libgcc="external-sourcery-toolchain"
PREFERRED_PROVIDER_nativesdk-libgcc="nativesdk-libgcc"