[cantarell-fonts] Fix parallel build.

[Nikolaus Waxweiler <nwaxweiler src gnome org>]

commit e2c2c3afe916947a521aa5310eabb9ada25d486f
Author: Nikolaus Waxweiler <madigens gmail com>
Date:   Thu Jan 7 00:34:18 2016 +0100

    Fix parallel build.

 otf/Makefile.am |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)
---
diff --git a/otf/Makefile.am b/otf/Makefile.am
index 2cf0f82..3abf0de 100644
--- a/otf/Makefile.am
+++ b/otf/Makefile.am
@@ -7,8 +7,10 @@ font_DATA = \
        Cantarell-Bold-Oblique.otf
 
 if SOURCE_REBUILD
-%.otf: $(top_srcdir)/src/%.sfdir
+$(filter-out %-Oblique.otf,$(font_DATA)): %.otf: $(top_srcdir)/src/%.sfdir
        /usr/bin/env fontforge -script $(top_srcdir)/scripts/generate.sh "$^"
+
+$(filter %-Oblique.otf,$(font_DATA)): %.otf: ;
 endif
 
 EXTRA_DIST = $(font_DATA)