build: build plugins and examples in parallel where possible

common @ ba33d1f3

-Subproject commit c1d07dd16cdb95e2cc83ced327d33cebab0fcf3d
+Subproject commit ba33d1f3cf0b9143963f13dd1ea05c93b1db8864

ext/Makefile.am

@@ -168,3 +168,5 @@ DIST_SUBDIRS = \
 	speex \
 	taglib \
 	wavpack
+
+include $(top_srcdir)/common/parallel-subdirs.mak

gst/Makefile.am

 SUBDIRS = $(GST_PLUGINS_SELECTED)
 DIST_SUBDIRS = $(GST_PLUGINS_ALL)
+
+include $(top_srcdir)/common/parallel-subdirs.mak

sys/Makefile.am

@@ -73,3 +73,5 @@ endif
 SUBDIRS=$(DIRECTSOUND_DIR) $(OSS_DIR) $(OSX_AUDIO_DIR) $(OSX_VIDEO_DIR) $(SUNAUDIO_DIR) $(V4L2_DIR) $(XIMAGE_DIR)
 
 DIST_SUBDIRS=directsound oss osxaudio osxvideo sunaudio v4l2 waveform ximage
+
+include $(top_srcdir)/common/parallel-subdirs.mak

tests/examples/Makefile.am

 SUBDIRS = audiofx equalizer level rtp shapewipe spectrum v4l2
 
 DIST_SUBDIRS = audiofx equalizer level rtp shapewipe spectrum v4l2
+
+include $(top_srcdir)/common/parallel-subdirs.mak