doc: Fix GHC clean rule

Apparently GHC's build system doesn't permit wildcards in clean paths.

Author: bgamari

CHANGES

@@ -4,6 +4,8 @@ Changes in version 2.17.1
 
  * Fixed Makefile for GHC installation
 
+ * Fixed clean rule of GHC Makefile
+
 Changes in version 2.17.0 (not released)
 
  * Support typesetting of mathematical expressions via Mathjax (#397)

doc/ghc.mk

@@ -13,7 +13,7 @@
 ifeq "$(BUILD_SPHINX_HTML)" "YES"
 html : html_utils/haddock/doc
 
-$(eval $(call clean-target,utils/haddock/doc,sphinx,utils/haddock/doc/haddock utils/haddock/doc/.build-*))
+$(eval $(call clean-target,utils/haddock/doc,sphinx,utils/haddock/doc/haddock utils/haddock/doc/.build-html utils/haddock/doc/.build-pdf))
 $(eval $(call all-target,utils/haddock/doc,html_utils/haddock/doc))
 INSTALL_HTML_DOC_DIRS += utils/haddock/doc/haddock
 endif