gcc-runtime: Fix QA issue

gcc-runtime: Fix QA issue

ERROR: gcc-runtime-6.3.0-r0 do_package: QA Issue: gcc-runtime: Files/directories were installed but not shipped in any package:
  /usr/lib/libmpxwrappers.la
Please set FILES such that these items are packaged. Alternatively if they are unneeded, avoid installing them or delete them within do_install.
gcc-runtime: 1 installed and not shipped files. [installed-vs-shipped]

(From OE-Core rev: 3658da86e57dc87ac3957b05f853a7f1a56bfab2)

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>