main/meson: do not set b_ndebug an abuild-meson

The `b_ndebug` meson option is equivalent to setting `-DNDEBUG` in
`CXXFLAGS`/`CFLAGS` in `/etc/abuild.conf`. The `NDEBUG` preprocessor
macro disable alls assert(3) statements. If we really believe that enabling
this by default is a good idea we should do so through the
`CXXFLAGS`/`CFLAGS` variable to ensure this is activated for all aports,
not just meson aports.
7 jobs for !7970 with meson-ndebug in 3 minutes and 45 seconds (queued for 3 seconds)
latest detached
Status Job ID Name Coverage
  Lint
passed #118222
x86_64 docker-alpine
lint

00:00:20

 
  Build
passed #118227
aarch64 ci-build docker-alpine
build-aarch64

00:01:03

passed #118228
armv7 ci-build docker-alpine
build-armv7

00:00:38

passed #118226
ppc64le ci-build docker-alpine
build-ppc64le

00:01:19

passed #118225
s390x ci-build docker-alpine
build-s390x

00:00:25

passed #118224
x86 ci-build docker-alpine
build-x86

00:00:26

passed #118223
x86_64 ci-build docker-alpine
build-x86_64

00:00:28