[OE-core] vmdk images with musl libc

[Andre McCurdy]

It's currently not possible to build a vmdk image when TCLIBC = "musl"
due to the following dependencies:

  do_bootdirectdisk -> syslinux -> mtools -> glibc-gconv-ibm850

Creating an mtools .bbappend containing:

  RDEPENDS_${PN}_libc-musl = ""
  RRECOMMENDS_${PN}_libc-musl = ""

seems to be a workaround.

Does anyone see a better solution?