[PATCH v2] perf: Fix clean error

[Lei YU <mine260309@gmail.com>]

When make perf with -O, it gets error when make clean with below log:

 $ make -C tools/perf O=<output/dir> # OK
 $ make -C tools/perf O=<output/dir> clean # Got below error

    find: cannot delete ‘<output/dir>/builtin-script.o’: No such file or directory
    find: cannot delete ‘<output/dir>/.subcmd-config.o.cmd’: No such file or directory
    ...
    Makefile:38: recipe for target 'clean' failed
    make[2]: *** [clean] Error 1
    make[1]: *** [fixdep-clean] Error 2
    Makefile:90: recipe for target 'clean' failed
    make: *** [clean] Error 2

It happens because both fixdep-clean and libsubcmd-clean will delete
files by `find`, where libsubcmd-clean uses `| xargs $(RM)` and
fixdep-clean uses `-delete`.
When a file is find by fixdep-clean, and tries to delete it, it's found
that the file does not exist because it is deleted by libsubcmd-clean.

This commit changes the delete method of fixdep-clean to use
`| xargs $(RM)` as well, where RM is defined as `rm -f` so it does not
return error when file does not exist.

Signed-off-by: Lei YU <mine260309@gmail.com>

---
v2: Fix missing "make clean" in commit message
---
 tools/build/Makefile | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/build/Makefile b/tools/build/Makefile
index 5edf65e..ae38db2 100644
--- a/tools/build/Makefile
+++ b/tools/build/Makefile
@@ -18,6 +18,7 @@ $(call allow-override,LD,$(CROSS_COMPILE)ld)
 HOSTCC ?= gcc
 HOSTLD ?= ld
 HOSTAR ?= ar
+RM = rm -f
 
 export HOSTCC HOSTLD HOSTAR
 
@@ -36,7 +37,7 @@ all: $(OUTPUT)fixdep
 
 clean:
 	$(call QUIET_CLEAN, fixdep)
-	$(Q)find $(if $(OUTPUT),$(OUTPUT),.) -name '*.o' -delete -o -name '\.*.cmd' -delete -o -name '\.*.d' -delete
+	$(Q)find $(if $(OUTPUT),$(OUTPUT),.) -name '*.o' -o -name '\.*.cmd' -o -name '\.*.d' | xargs $(RM)
 	$(Q)rm -f $(OUTPUT)fixdep
 
 $(OUTPUT)fixdep-in.o: FORCE
-- 
2.7.4