build: Add missing line continuation
build: Add missing line continuation

When -lrt was added, it was missing a '\' at the end of line. Add it.

Cc: Tim Gore <574638b6c8be9618c62b9975be7a73fefbc6d4f1@intel.com>
Cc: Thomas Wood <b9025d6a953b68f894a0f6a80fd2af6d55b0badd@intel.com>
Signed-off-by: Damien Lespiau <64bd3cb94f359c1a3ce68dae5e26b40578526277@intel.com>

chenxianqin/intel-gpu-tools,dlespiau/checkmate-test-igt,mv0/intel-gpu-tools,mv0/intel-gpu-tools,tiagovignatti/intel-gpu-tools,dlespiau/checkmate-test-igt,chenxianqin/intel-gpu-tools,dlespiau/checkmate-test-igt,dlespiau/checkmate-test-igt,chenxianqin/intel-gpu-tools,mv0/intel-gpu-tools,tiagovignatti/intel-gpu-tools,tiagovignatti/intel-gpu-tools,tiagovignatti/intel-gpu-tools,chenxianqin/intel-gpu-tools,mv0/intel-gpu-tools