perf tools: Fix perf builds with clang support

perf tools: Fix perf builds with clang support

For libclang, some distro packages provide static libraries (.a) while
some provide shared libraries (.so). Currently, perf code can only be
linked with static libraries. This makes perf build possible for both
cases.

Signed-off-by: Sandipan Das <sandipan@linux.vnet.ibm.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Fixes: d58ac0bf8d1e ("perf build: Add clang and llvm compile and linking support")
Link: http://lkml.kernel.org/r/20180404180419.19056-1-sandipan@linux.vnet.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>