Defaultly gst-plugins-bad will configured with option --enable-rsvg.
Besides, it will check if librsvg really exists by certain configure
code.
Therefore there will be a certain race condition that, during
librsvg's populate_sysroot, gst-plugins-bad's do_compile will find
some header files are still not exists though its configure says the
library is supported.
Explicitly add librsvg as gst-plugins-bad's dependency could solve
this issue.
