[ng] header vars: fix comment on why DESTDIR is not explicitly initialized

* lib/am/header-vars.am (DESTDIR): It's because we want to allow it to
be defined from the environment, for compatibility with mainline Automake.
For better clarity, define an (empty) default with the line "DESTDIR ?=",
instead of with the commented-out definition "# DESTDIR=".

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>

diff --git a/lib/am/header-vars.am b/lib/am/header-vars.am
index a27a8fba9a71bdada6f42da444a8be97fb96f517..ca9450d6a9f5a3f6e0925770c67ba547b2b8c0de 100644 (file)
--- a/lib/am/header-vars.am
+++ b/lib/am/header-vars.am
@@ -119,13 +119,9 @@ am__ensure_target_dir_exists = $(call am__ensure_dir_exists,$(@D))
 am.vpath.rewrite = \
   $(firstword $(wildcard $(strip $(1))) $(srcdir)/$(strip $(1)))
 
-## We used to define this.  However, we don't because vendor makes
-## (e.g., Solaris, Irix) won't correctly propagate variables that are
-## defined in Makefile.  This particular variable can't be correctly
-## defined by configure (at least, not the current configure), so we
-## simply avoid defining it to allow the user to use this feature with
-## a vendor make.
-## DESTDIR =
+# make this overridable from the environment, for better compatibility
+# with mainline Automake.
+DESTDIR ?=
 
 ## Tell whether make is running in "dry mode".  It is either 'true' or
 ## 'false', so that it can be easily used in shell code as well as in