meson: update required version

In meson 0.58 the `get_variable` was enhanced to no longer require the
`pkgconfig` keyword argument, but instead it uses a positional argument
which applies to all search-types.  This repository is already using
a variant which is only supported on meson 0.58 (or later) so ensure
the 0.58 version is required.

Change-Id: I782f745d4a0676fa35f80712cf5bc08b79f7cbdf
Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
1 file changed