[gnome-builder] doc: add uninstall hooks for docs

[Christian Hergert <chergert src gnome org>]

commit 8e145bbe6714a8b6b30054539fcb0335ae17df69
Author: Christian Hergert <chergert redhat com>
Date:   Tue Mar 14 01:32:55 2017 -0700

    doc: add uninstall hooks for docs

 doc/Makefile.am |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/doc/Makefile.am b/doc/Makefile.am
index 40ace4f..c76893a 100644
--- a/doc/Makefile.am
+++ b/doc/Makefile.am
@@ -66,6 +66,9 @@ install-data-hook:
                cp -a $(srcdir)/html/* "$(DESTDIR)$(docdir)/html/" ; \
        fi
 
+uninstall-local:
+       rm -rf "$(DESTDIR)$(docdir)/html/"
+
 GITIGNOREFILES = _build
 
 -include $(top_srcdir)/git.mk