When starting a qemu binary directly from the build directory and that
dir is located outside the source files, the search for bios files
fails. Fix this by linking them from the build to the source directory.
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>