Use --depth 1 for submodule updates to prevent cloning of unneeded history

Author: TShapinsky

Makefile.in

@@ -347,7 +347,7 @@ endif
 $(srcdir)/%/.git:
 	cd $(srcdir) && \
 	flock `git rev-parse --git-dir`/config git submodule init $(dir $@) && \
-	flock `git rev-parse --git-dir`/config git submodule update --progress $(dir $@)
+	flock `git rev-parse --git-dir`/config git submodule update --progress --depth 1 $(dir $@)
 
 stamps/install-host-gcc: $(GCC_SRCDIR) $(GCC_SRC_GIT)
 	if test -f $</contrib/download_prerequisites && test "@NEED_GCC_EXTERNAL_LIBRARIES@" = "true"; then cd $< && ./contrib/download_prerequisites; fi