libclc: Pass system libraries to the linker after llvm libraries

Summary:
The llvm libraries depend on the symbols in the system libaries, so
the system libraries need to be added after.

Reviewers: jvesely

Reviewed By: jvesely

Subscribers: mgorny, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D78535

(cherry picked from commit 174c41de)