build: fix variable name in dependency error message
build: fix variable name in dependency error message

The variable name in the error message had an extra '_' which caused
an actual meson error when the message would otherwise be printed to
give meaningful information about what was going wrong.

Fixes: 203b61dc5e18 ("build: improve error message for missing dependency")
Cc: stable@dpdk.org

Signed-off-by: Bruce Richardson <66b9e8e8fbd5e9f41f91b0af050876182ce9d0e4@intel.com>
Acked-by: Luca Boccassi <020748dc039465edc3ee6f30c530b21164cdce27@debian.org>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk