make -C tools clean failure on older systems

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Hi,

	In:

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commit 67d8712dcc70aa16d8e14a52eb73870e3cbddfc2
Author: Shuah Khan <shuahkh@osg.samsung.com>
Date:   Wed Mar 18 11:57:39 2015 -0600

    selftests: Fix build failures when invoked from kselftest target

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You cleaned two variables using different methods, any reason for that?

I asked because the 'undefine' method causes it to fail in older
systems:

[acme@rhel5 linux]$ make -C tools/ clean
<SNIP>
  CLEAN    python
make[1]: Leaving directory `/home/acme/git/linux/tools/perf'
  DESCEND  testing/selftests
make[1]: Entering directory
`/home/acme/git/linux/tools/testing/selftests'
Makefile:30: *** missing separator.  Stop.
make[1]: Leaving directory
`/home/acme/git/linux/tools/testing/selftests'
make: *** [selftests_clean] Error 2
make: Leaving directory `/home/acme/git/linux/tools'

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

[acme@rhel5 linux]$ make --version
GNU Make 3.81
Copyright (C) 2006  Free Software Foundation, Inc.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.

This program built for x86_64-redhat-linux-gnu
[acme@rhel5 linux]$

Wonder if it would be ok to use:

diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 95abddcd7839..f76830643086 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -27,7 +27,7 @@ TARGETS_HOTPLUG += memory-hotplug
 # Makefile to avoid test build failures when test
 # Makefile doesn't have explicit build rules.
 ifeq (1,$(MAKELEVEL))
-undefine LDFLAGS
+override LDFLAGS =
 override MAKEFLAGS =
 endif
 
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- Arnaldo