[PATCH 4.1 06/11] perf tools: Fix build breakage if prefix= is specified

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

4.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Lukas Wunner <lukas@wunner.de>

commit 75e84ab906ef8935cff3df3d8929f1bafea81599 upstream.

Invoking Makefile.perf with prefix= breaks the build since Makefile.perf
hands that variable down to Makefile.build where it overrides

    prefix       := $(subst ./,,$(OUTPUT)$(dir)/)

leading to errors like this:

    No rule to make target '/usrabspath.o', needed by '/usrlibperf-in.o'

Signed-off-by: Lukas Wunner <lukas@wunner.de>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Fixes: c819e2cf2eb6f65d3208d195d7a0edef6108d5
Link: http://lkml.kernel.org/r/5582c48a.84a22b0a.a918.5285SMTPIN_ADDED_MISSING@mx.google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 tools/build/Makefile.build |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/tools/build/Makefile.build
+++ b/tools/build/Makefile.build
@@ -94,12 +94,12 @@ obj-y        := $(patsubst %/, %/$(obj)-
 subdir-obj-y := $(filter %/$(obj)-in.o, $(obj-y))
 
 # '$(OUTPUT)/dir' prefix to all objects
-prefix       := $(subst ./,,$(OUTPUT)$(dir)/)
-obj-y        := $(addprefix $(prefix),$(obj-y))
-subdir-obj-y := $(addprefix $(prefix),$(subdir-obj-y))
+objprefix    := $(subst ./,,$(OUTPUT)$(dir)/)
+obj-y        := $(addprefix $(objprefix),$(obj-y))
+subdir-obj-y := $(addprefix $(objprefix),$(subdir-obj-y))
 
 # Final '$(obj)-in.o' object
-in-target := $(prefix)$(obj)-in.o
+in-target := $(objprefix)$(obj)-in.o
 
 PHONY += $(subdir-y)