bug#56749: modernize bootstrap.conf

[Paul Eggert]

Thanks for the heads-up. I installed the attached patch to gzip and 
updated the bootstrap script to current Gnulib.diff --git a/README-hacking b/README-hacking
index 60e40ca..4af67f4 100644
--- a/README-hacking
+++ b/README-hacking
@@ -63,6 +63,17 @@ and the Git master copy:
 
 should output no difference.
 
+If you have already bootstrapped, you can redo it in two phases:
+
+        $ # 1. Fetch auxiliary files from the network.
+        $ ./autopull.sh
+        $
+        $ # 2. Generate files locally.
+        $ ./autogen.sh
+
+Separating the phases can be useful for reproducible builds, and for
+applying local modifications between the two phases.
+
 Enjoy!
 
 [*] By default GCC warnings are enabled when building from Git.
diff --git a/bootstrap.conf b/bootstrap.conf
index d2363dc..9a67bc2 100644
--- a/bootstrap.conf
+++ b/bootstrap.conf
@@ -76,9 +76,6 @@ gnulib_tool_option_extras="\
 "
 
 
-# Create build-aux, since 'bootstrap' won't do that for us.
-mkdir -p build-aux
-
 # Build prerequisites
 buildreq="\
 autoconf   2.61
@@ -98,4 +95,6 @@ bootstrap_epilogue()
 }
 
 # Automake requires that ChangeLog exist.
-touch ChangeLog || exit 1
+bootstrap_post_import_hook() {
+  touch ChangeLog || exit
+}