devtools: reduce build test verbosity
devtools: reduce build test verbosity

The default verbosity of test-meson-builds.sh is to be quiet.
In order to better apply the verbosity policy, some file descriptors
are open to redirect to stdout or /dev/null accordingly.

The target variable and meson/ninja commands are printed in verbose modes.
The installation commands are printed only in very verbose mode.
The examples build commands are printed only in very verbose mode.

Signed-off-by: Thomas Monjalon <5f50a84c1fa3bcff146405017f36aec1a10a9e38@monjalon.net>
Acked-by: David Marchand <f28529695cfa9e3e1eb84e7072aa626af4abb18e@redhat.com>
Acked-by: Bruce Richardson <66b9e8e8fbd5e9f41f91b0af050876182ce9d0e4@intel.com>

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