Log Message:
devel/meson/build.mk: Change MESON_CROSS_BINARIES -> MESON_BINARIES.

Use this with native builds too, via --native-file, if enabled.  No
change to builds that don't opt into using MESON_BINARIES.

Usage:

MESON_BINARIES+=	foo bar
MESON_BINARY.foo=	${TOOLBASE}/libexec/foo
MESON_BINARY_KEY.bar=	${PREFIX}/bin/bar
MESON_BINARY.bar=	${TOOLBASE}/bin/bar

Assuming PREFIX=/usr/pkg and TOOLBASE=/home/dev/pkg, this will build
with the following [binaries] section in the meson --native-file or
--cross-file:

[binaries]
foo = '/home/dev/pkg/libexec/foo'
/usr/pkg/bin/bar = '/home/dev/pkg/libexec/bar'