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: David 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.uk
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
bf35182ffc