Improve setup for 'dlg' library.

* autogen.sh (copy_submodule_file), builds/toplevel.mk: Redirect
stderr to `/dev/null`.

* builds/toplevel.mk: Move code block to handle 'dlg' stuff into
`check_platform` conditional.
Also fix wildcard expressions for guarding `git submodule` commands.
Also make file copying work with non-Unix platforms (untested).

ChangeLog

@@ -1,3 +1,15 @@
+2020-12-02  Werner Lemberg  <wl@gnu.org>
+
+	Improve setup for 'dlg' library.
+
+	* autogen.sh (copy_submodule_file), builds/toplevel.mk: Redirect
+	stderr to `/dev/null`.
+
+	* builds/toplevel.mk: Move code block to handle 'dlg' stuff into
+	`check_platform` conditional.
+	Also fix wildcard expressions for guarding `git submodule` commands.
+	Also make file copying work with non-Unix platforms (untested).
+
 2020-12-01  Werner Lemberg  <wl@gnu.org>
 
 	[build] Use gcc (and clang) in C99 mode.

autogen.sh

@@ -166,7 +166,7 @@ chmod +x ./configure
 copy_submodule_files ()
 {
   echo "Copying files from \`submodules/dlg' to \`src/dlg'"
-  mkdir src/dlg/dlg
+  mkdir src/dlg/dlg 2> /dev/null
   cp $DLG_INC_DIR/dlg.h src/dlg/dlg
   cp $DLG_INC_DIR/output.h src/dlg/dlg
   cp $DLG_SRC_DIR/* src/dlg

builds/toplevel.mk

@@ -103,23 +103,6 @@ ifneq ($(findstring setup,$(MAKECMDGOALS)),)
   check_platform := 1
 endif
 
-# For builds directly from the git repository we need to copy files
-# from `submodule/dlg' to `src/dlg'.
-#
-ifeq ($(wildcard src/dlg/dlg.*),)
-  ifeq ($(wildcard submodules/dlg/dlg.*),)
-    $(info Checking out submodule in `submodules/dlg')
-    $(shell git submodule init)
-    $(shell git submodule update)
-  endif
-
-  $(info Copying files from `submodules/dlg' to `src/dlg')
-  $(shell mkdir src/dlg/dlg)
-  $(shell cp submodules/dlg/include/dlg/dlg.h src/dlg/dlg)
-  $(shell cp submodules/dlg/include/dlg/output.h src/dlg/dlg)
-  $(shell cp submodules/dlg/src/dlg/dlg.c src/dlg/)
-endif
-
 # Include the automatic host platform detection rules when we need to
 # check the platform.
 #
@@ -129,6 +112,26 @@ ifdef check_platform
 
   include $(TOP_DIR)/builds/detect.mk
 
+  # For builds directly from the git repository we need to copy files
+  # from `submodule/dlg' to `src/dlg'.
+  #
+  ifeq ($(wildcard src/dlg/dlg.*),)
+    ifeq ($(wildcard submodules/dlg/*),)
+      $(info Checking out submodule in `submodules/dlg')
+      $(shell git submodule init)
+      $(shell git submodule update)
+    endif
+
+    $(info Copying files from `submodules/dlg' to `src/dlg')
+    $(shell mkdir $(subst /,$(SEP),src/dlg/dlg) $(NO_OUTPUT))
+    $(shell $(COPY) \
+      $(subst /,$(SEP),submodules/dlg/include/dlg/dlg.h src/dlg/dlg))
+    $(shell $(COPY) \
+      $(subst /,$(SEP),submodules/dlg/include/dlg/output.h src/dlg/dlg))
+    $(shell $(COPY) \
+      $(subst /,$(SEP),submodules/dlg/src/dlg/dlg.c src/dlg))
+  endif
+
   # This rule makes sense for Unix only to remove files created by a run of
   # the configure script which hasn't been successful (so that no
   # `config.mk' has been created).  It uses the built-in $(RM) command of