[BUGFIX PATCH v2] tools: Let O= makes handle a relative path with -C option

[Masami Hiramatsu <mhiramat@kernel.org>]

When I compiled tools/perf from top directory with the -C option,
the O= option didn't work correctly if I passed a relative path.

  $ make O=BUILD -C tools/perf/
  make: Entering directory '/home/mhiramat/ksrc/linux/tools/perf'
    BUILD:   Doing 'make -j8' parallel build
  ../scripts/Makefile.include:4: *** O=/home/mhiramat/ksrc/linux/tools/perf/BUILD does not exist.  Stop.
  make: *** [Makefile:70: all] Error 2
  make: Leaving directory '/home/mhiramat/ksrc/linux/tools/perf'

The O= directory existence check failed because the check
script ran in the build target directory instead of the
directory where I ran the make command.

To fix that, once change directory to $(PWD) and check O=
directory, since the PWD is set to where the make command
runs.

Fixes: c883122acc0d ("perf tools: Let O= makes handle relative paths")
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: stable@vger.kernel.org

---
 Changes in V2:
 - Fix tools/perf/Makefile because it has own O= pre-process.
 - Use tools/perf for example.
 - Add explicit Cc: stable@vger.kernel.org tag.
---
 tools/perf/Makefile            |    2 +-
 tools/scripts/Makefile.include |    4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/perf/Makefile b/tools/perf/Makefile
index 7902a5681fc8..b8fc7d972be9 100644
--- a/tools/perf/Makefile
+++ b/tools/perf/Makefile
@@ -35,7 +35,7 @@ endif
 # Only pass canonical directory names as the output directory:
 #
 ifneq ($(O),)
-  FULL_O := $(shell readlink -f $(O) || echo $(O))
+  FULL_O := $(shell cd $(PWD); readlink -f $(O) || echo $(O))
 endif
 
 #
diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include
index ded7a950dc40..6d2f3a1b2249 100644
--- a/tools/scripts/Makefile.include
+++ b/tools/scripts/Makefile.include
@@ -1,8 +1,8 @@
 # SPDX-License-Identifier: GPL-2.0
 ifneq ($(O),)
 ifeq ($(origin O), command line)
-	dummy := $(if $(shell test -d $(O) || echo $(O)),$(error O=$(O) does not exist),)
-	ABSOLUTE_O := $(shell cd $(O) ; pwd)
+	dummy := $(if $(shell cd $(PWD); test -d $(O) || echo $(O)),$(error O=$(O) does not exist),)
+	ABSOLUTE_O := $(shell cd $(PWD); cd $(O) ; pwd)
 	OUTPUT := $(ABSOLUTE_O)/$(if $(subdir),$(subdir)/)
 	COMMAND_O := O=$(ABSOLUTE_O)
 ifeq ($(objtree),)