gstreamer1: don't rely on a recent coreutils for relative symlink support

Fixes:
http://autobuild.buildroot.net/results/3ae/3ae368cfd0ecd7be4c7e864590ec5dbf79d576ac/
http://autobuild.buildroot.net/results/4c9/4c951f31984e0eff21fc165cb68065f527c237e6/

And many more.

The recent change to create the legacy gstconfig.h symlink using ln -srf
unfortunately breaks on older distributions as it was only added in
coreutils 8.16 (2012).

Instead, "manually" create the relative symlink.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/gstreamer1/gstreamer1/gstreamer1.mk

@@ -41,8 +41,8 @@ GSTREAMER1_DEPENDENCIES = libglib2 host-pkgconf host-bison host-flex
 # updated to look in the correct location.
 # Add a symlink to the legacy location
 define GSTREAMER1_LEGACY_CGSTCONFIG_H
-	ln -srf $(STAGING_DIR)/usr/lib/gstreamer-1.0/include/gst/gstconfig.h \
-	       $(STAGING_DIR)/usr/include/gstreamer-1.0/gst/gstconfig.h
+	cd $(STAGING_DIR)/usr/include/gstreamer-1.0/gst && \
+		ln -sf ../../../lib/gstreamer-1.0/include/gst/gstconfig.h .
 endef
 GSTREAMER1_POST_INSTALL_STAGING_HOOKS += GSTREAMER1_LEGACY_CGSTCONFIG_H