multipath-tools: Fix build failure due to GZIP make var

The multipath-tools makefiles use GZIP as a variable name but this is
also the name of the environment variable gzip uses to get its default
options.

Normally, this wouldn't get into the environment but nixpkgs exports
GZIP=-n in a setup hook. This in turn causes make to export its own
value for this variable. gzip objects to having -c in the environment
variable and aborts, causing the build to fail.

pkgs/os-specific/linux/multipath-tools/default.nix

@@ -17,8 +17,8 @@ stdenv.mkDerivation rec {
     ' libmultipath/defaults.h
     sed -i -e 's,\$(DESTDIR)/\(usr/\)\?,$(prefix)/,g' \
       kpartx/Makefile libmpathpersist/Makefile
-    sed -i -e "s,GZIP = .*, GZIP = gzip -9n -c," \
-      Makefile.inc
+    sed -i -e "s,GZIP,GZ," \
+      $(find * -name Makefile\*)
   '';
 
   nativeBuildInputs = [ gzip pkgconfig perl ];