Honour the O= flag that was passed to a higher level Makefile and then passed
down as part of a tool build.

To make this work, the top-level Makefile passes the original O= flag and
subdir=tools to the tools/Makefile, and that in turn passes
subdir=$(O)/$(subdir)/foodir when building tool foo in directory
$(O)/$(subdir)/foodir (where the intervening slashes aren't added if an
element is missing).

For example, take perf.  This is found in tools/perf/.  Assume we're building
into directory ~/zebra/, so we pass O=~/zebra to make.  Dependening on where
we run the build from, we see:

	make run in dir		$(OUTPUT) dir
	=======================	==================
	linux			~/zebra/tools/perf/
	linux/tools		~/zebra/perf/
	linux/tools/perf	~/zebra/

and if O= is not set, we get:

	make run in dir		$(OUTPUT) dir
	=======================	==================
	linux			linux/tools/perf/
	linux/tools		linux/tools/perf/
	linux/tools/perf	linux/tools/perf/

The output directories are created by the descend function if they don't
already exist.
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Cc: Borislav Petkov <bp@amd64.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1378.1352379110@warthog.procyon.org.ukSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Define a Makefile function that can be called with $(call ...) to wrap
the subdir make invocations in tools/Makefile.

This will allow us in the next patch to insert bits in there to honour
O= flags when called from the top-level Makefile.
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Cc: Borislav Petkov <bp@amd64.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1378.1352379110@warthog.procyon.org.ukSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

When I did a compile of perf using a relative path for the output
directory, the build failed when it tried to compile libtraceevent. This
is because it continues to use the same relative path when the new
working directory is in a different path.

    SUBDIR ../lib/traceevent/
/bin/sh: line 0: cd: ../../../nobackup/perf/: No such file or directory
Makefile:74: *** output directory "../../../nobackup/perf/" does not exist.  Stop.
make: *** [../../../nobackup/perf///libtraceevent.a] Error 2

Make the path used an absolute path when building perf with O=.

Boris:

Teach Makefile to check whether the supplied O= directory exists and
bail out if not. Reportedly, kernel dudes are idiots and need to be
guarded so as not to shoot themselves in the foot when playing in the
sandbox.
Signed-off-by: NBorislav Petkov <borislav.petkov@amd.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120815163923.GD15989@aftab.osrc.amd.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Have building perf also build libtraceevent.a. Currently, perf does
not use the code within libtraceevent.a, but it soon will.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Arun Sharma <asharma@fb.com>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>

Use += instead of the bash syntax, as Sam Ravnborg suggests. Also, sort
the -W options alphabetically and (... keep them sorted).
Suggested-by: NSam Ravnborg <sam@ravnborg.org>
Signed-off-by: NBorislav Petkov <borislav.petkov@amd.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Sam Ravnborg <sam@ravnborg.org>
Link: http://lkml.kernel.org/r/1334162178-17152-3-git-send-email-bp@amd64.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Put generic enough build settings which could be reused by other tools
into a common Makefile.include file.

This commit reintroduces QUIET_SUBDIR{0,1} (see a3d1ee10) which are
going to be used in the following patches.
Signed-off-by: NBorislav Petkov <borislav.petkov@amd.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Sam Ravnborg <sam@ravnborg.org>
Link: http://lkml.kernel.org/r/1334162178-17152-2-git-send-email-bp@amd64.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>