perf jit: Fix build issue on Ubuntu

When building on Ubuntu 16.04, I get the following error:

Makefile:49: *** the openjdk development package appears to me missing, install and try again.  Stop.

The problem is that update-java-alternatives has multiple spaces between
fields, and cut treats each space as a new delimiter:

java-1.8.0-openjdk-ppc64el     1081       /usr/lib/jvm/java-1.8.0-openjdk-ppc64el

Fix this by using awk, which handles this fine.

Signed-off-by: Anton Blanchard <anton@samba.org>
Reviewed-by: Stephane Eranian <eranian@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1476325243-15788-1-git-send-email-anton@ozlabs.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/jvmti/Makefile

@@ -36,7 +36,7 @@ SOLIBEXT=so
 # The following works at least on fedora 23, you may need the next
 # line for other distros.
 ifneq (,$(wildcard /usr/sbin/update-java-alternatives))
-JDIR=$(shell /usr/sbin/update-java-alternatives -l | head -1 | cut -d ' ' -f 3)
+JDIR=$(shell /usr/sbin/update-java-alternatives -l | head -1 | awk '{print $$3}')
 else
   ifneq (,$(wildcard /usr/sbin/alternatives))
     JDIR=$(shell alternatives --display java | tail -1 | cut -d' ' -f 5 | sed 's%/jre/bin/java.%%g')