tools build tests: Don't hardcode gcc name

Use $(CC) instead of harcoded gcc binary name.

Signed-off-by: David Carrillo-Cisneros <davidcc@google.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Paul Turner <pjt@google.com>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/20170827075442.108534-2-davidcc@google.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>