tools build feature: Check if libaio is available

This will be used by 'perf record' to speed up reading the perf ring
buffer.

Committer testing:

$ make -C tools/perf O=/tmp/build/perf
make: Entering directory '/home/acme/git/perf/tools/perf'
BUILD: Doing 'make -j8' parallel build

Auto-detecting system features:
... dwarf: [ on ]
... dwarf_getlocations: [ on ]
... glibc: [ on ]
... gtk2: [ OFF ]
... libaudit: [ OFF ]
... libbfd: [ OFF ]
... libelf: [ on ]
... libnuma: [ OFF ]
... numa_num_possible_cpus: [ OFF ]
... libperl: [ OFF ]
... libpython: [ OFF ]
... libslang: [ on ]
... libcrypto: [ on ]
... libunwind: [ on ]
... libdw-dwarf-unwind: [ on ]
... zlib: [ on ]
... lzma: [ on ]
... get_cpuid: [ on ]
... bpf: [ on ]
... libaio: [ on ]

$ ls -la /tmp/build/perf/feature/test-libaio.*
-rwxrwxr-x. 1 acme acme 18296 Nov 26 08:49 /tmp/build/perf/feature/test-libaio.bin
-rw-rw-r--. 1 acme acme 1165 Nov 26 08:49 /tmp/build/perf/feature/test-libaio.d
-rw-rw-r--. 1 acme acme 0 Nov 26 08:49 /tmp/build/perf/feature/test-libaio.make.output
$
$ grep -i aio /tmp/build/perf/FEATURE-DUMP
feature-libaio=1
$

Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Reviewed-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/5fcda10c-6c63-68df-383a-c6d9e5d1f918@linux.intel.com
[ split from a larger patch ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>