Clarify the use of -Doption and alternatives [skip ci]
Clarify the use of -Doption and alternatives [skip ci]

The -Doption=value style argument works for all builtin options,
and compiler options passed to meson. And some universal options,
have additional ways to be passed. However, base options (and compiler
options) do not have exactly the same ways of passing as universal
options.

This change adds a few pieces of information, which might get lost,
if the manual is not read serially.

[skip ci]

jpakkane/meson,QuLogic/meson,QuLogic/meson,mesonbuild/meson,pexip/meson,pexip/meson,QuLogic/meson,mesonbuild/meson,QuLogic/meson,jpakkane/meson,pexip/meson,jpakkane/meson,jpakkane/meson,jpakkane/meson,pexip/meson,mesonbuild/meson,jpakkane/meson,QuLogic/meson,jpakkane/meson,QuLogic/meson,pexip/meson,mesonbuild/meson,mesonbuild/meson,jpakkane/meson,pexip/meson,mesonbuild/meson,pexip/meson,QuLogic/meson,mesonbuild/meson,mesonbuild/meson,pexip/meson,jpakkane/meson,pexip/meson,mesonbuild/meson,mesonbuild/meson,QuLogic/meson,QuLogic/meson,pexip/meson