perf build: Force llvm/clang test compile output to .make.output

perf build: Force llvm/clang test compile output to .make.output

So we can see the output of feature compile in following files:

  tools/build/feature/test-llvm.make.output
  tools/build/feature/test-llvm-version.make.output
  tools/build/feature/test-clang.make.output

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20180307155020.32613-20-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>