kbuild: make namespace.pl CROSS_COMPILE happy

Using the fixed path to /usr/bin/{nm,objdump} does not allow
CROSS_COMPILE environments to use namespace.pl. This patch causes
namespace.pl to use $NM and $OBJDUMP if defined or fall back to the nm
and objdump found in the path.
Signed-off-by: Aaron Brooks <aaron.brooks@sicortex.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

scripts/namespace.pl

@@ -66,8 +66,8 @@ require 5;	# at least perl 5
 use strict;
 use File::Find;
 
-my $nm = "/usr/bin/nm -p";
-my $objdump = "/usr/bin/objdump -s -j .comment";
+my $nm = ($ENV{'NM'} || "nm") . " -p";
+my $objdump = ($ENV{'OBJDUMP'} || "objdump") . " -s -j .comment";
 my $srctree = "";
 my $objtree = "";
 $srctree = "$ENV{'srctree'}/" if (exists($ENV{'srctree'}));