perf jvmti: Add check for java alternatives cmd in Makefile

This patch modifies the jvmti makefile to check if the
/usr/sbin/java-update-alternatives utility is present.  If so, then use
it, if not then use the altenatives command.

This helps handle the difference between Ubuntu and Fedora Linux
distributions.

Signed-off-by: Stephane Eranian <eranian@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1455604661-9357-1-git-send-email-eranian@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/jvmti/Makefile

@@ -35,8 +35,12 @@ SOLIBEXT=so
 
 # The following works at least on fedora 23, you may need the next
 # line for other distros.
+ifeq (,$(wildcard /usr/sbin/update-java-alternatives))
 JDIR=$(shell alternatives --display java | tail -1 | cut -d' ' -f 5 | sed 's%/jre/bin/java.%%g')
-#JDIR=$(shell /usr/sbin/update-java-alternatives -l | head -1 | cut -d ' ' -f 3)
+else
+JDIR=$(shell /usr/sbin/update-java-alternatives -l | head -1 | cut -d ' ' -f 3)
+endif
+
 # -lrt required in 32-bit mode for clock_gettime()
 LIBS=-lelf -lrt
 INCDIR=-I $(JDIR)/include -I $(JDIR)/include/linux