[libmediaart] build: Fixed continuous build failure that was detected

[Martyn James Russell <mr src gnome org>]

commit 585df2708eeceb410415ab8a0a5c53e8743c4c26
Author: Martyn Russell <martyn lanedo com>
Date:   Fri Aug 15 11:40:58 2014 +0100

    build: Fixed continuous build failure that was detected
    
    AutoMake warning += vs = for EXTRA_DIST/CLEANFILES

 Makefile.am |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/Makefile.am b/Makefile.am
index 8155f85..d01d44a 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -12,13 +12,13 @@ pkgconfigdir = $(libdir)/pkgconfig
 libmediaart-$(LIBMEDIAART_API_VERSION).pc: libmediaart.pc
        cp $< $@
 
-EXTRA_DIST = \
+EXTRA_DIST += \
        libmediaart.doap \
        libmediaart.pc.in \
         tap-driver.sh \
         tap-test
 
-CLEANFILES = \
+CLEANFILES += \
        libmediaart- LIBMEDIAART_API_VERSION@.pc
 
 DISTCHECK_CONFIGURE_FLAGS =                            \