The GNU C library version 2.26 included in Yocto Project 2.4 is licensed under the Lesser General Public License v2.1 (LGPLv2.1), which allows dynamic linking without license inheritance. So your proprietary code can dynamically link with glibc, but of course you still have to comply with the LGPL with regard to glibc. Note, however, that statically linking your application would pollute it with the LGPL.