perf tools: Warn the user about how to enable libunwind support

When one has libunwind installed somewhere the perf tools build process
doesn't expects it to be, this happens:

  [acme@ssdandy linux]$ make O=/tmp/build/perf -C tools/perf/ install-bin
  make: Entering directory `/home/acme/git/linux/tools/perf'
    BUILD:   Doing 'make -j8' parallel build
  config/Makefile:312: No libunwind found, disabling post unwind support.  Please install libunwind-dev[el] >= 1.1

  Auto-detecting system features:
  <SNIP>
  ...                     libunwind: [ OFF ]

Change the message so that it tells how to use a non-standard libunwind
install directory:

  config/Makefile:312: No libunwind found, disabling post unwind support.  Please install libunwind-dev[el] >= 1.1 and/or set LIBUNWIND_DIR

  [acme@ssdandy linux]$ make LIBUNWIND_DIR=/opt/libunwind-git/ O=/tmp/build/perf -C tools/perf/ install-bin
  make: Entering directory `/home/acme/git/linux/tools/perf'
    BUILD:   Doing 'make -j8' parallel build

  Auto-detecting system features:
  <SNIP>
  ...                     libunwind: [ on  ]

Acked-by: Jiri Olsa <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Mike Galbraith <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Stephane Eranian <[email protected]>
Link: http://lkml.kernel.org/n/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

0 files changed, 0 insertions, 0 deletions