protobuf: fix ptest compile errors
protobuf: fix ptest compile errors

While buiding protobuf ptest on Centos 6.4, the build
failed with errors:

...libprotobuf.so: undefined reference to `memcpy@GLIBC_2.14'

This is due to protobuf.pc still contains /usr/lib64
as libdir which are not good for cross compiling.
Replace it with proper sysroot path.

Signed-off-by: Zibo Zhao <99dbeb4b887294763abd70068a3d1e6efd8e1f5a@windriver.com>
Signed-off-by: Bruce Ashfield <284cc737d174a260eec2a2a6324a304f84b1ae0f@windriver.com>

lgirdk/meta-virtualization,lgirdk/meta-virtualization,cardoe/meta-virtualization,lgirdk/meta-virtualization,lgirdk/meta-virtualization,cardoe/meta-virtualization,rcwoolley/meta-virtualization,cardoe/meta-virtualization,cjp256/meta-virtualization,fbertux/meta-virtualization,fbertux/meta-virtualization,cjp256/meta-virtualization,cjp256/meta-virtualization,lgirdk/meta-virtualization,fbertux/meta-virtualization