Fix OpenCL/CUDA link order in .pc file

CUDA library defines some OpenCL symbols...

libstarpu.pc.in

@@ -23,7 +23,7 @@ Name: starpu
 Description: offers support for heterogeneous multicore architecture
 Version: @PACKAGE_VERSION@
 Cflags: -I${includedir}/starpu/@STARPU_EFFECTIVE_VERSION@ @STARPU_CUDA_CPPFLAGS@ -DSTARPU_USE_DEPRECATED_API
-Libs: -L${libdir} -lstarpu-@STARPU_EFFECTIVE_VERSION@ @STARPU_CUDA_LDFLAGS@ @STARPU_OPENCL_LDFLAGS@
+Libs: -L${libdir} -lstarpu-@STARPU_EFFECTIVE_VERSION@ @STARPU_OPENCL_LDFLAGS@ @STARPU_CUDA_LDFLAGS@
 Libs.private: @LDFLAGS@ @LIBS@
 Requires: @HWLOC_REQUIRES@
 Requires.private: @GORDON_REQUIRES@