Return code 0 when builddir is already configured
Return code 0 when builddir is already configured

This is a regression in Meson 0.48.0, commit 674ae46, Meson used to
exit(0) when running setup command in a builddir already configured.
Changing to exit(1) breaks some build tools that does "meson builddir
&& ninja -C builddir".

Closes #4247.

jpakkane/meson,becm/meson,pexip/meson,becm/meson,pexip/meson,jpakkane/meson,MathieuDuponchelle/meson,pexip/meson,MathieuDuponchelle/meson,mesonbuild/meson,MathieuDuponchelle/meson,MathieuDuponchelle/meson,pexip/meson,jpakkane/meson,mesonbuild/meson,becm/meson,mesonbuild/meson,pexip/meson,pexip/meson,pexip/meson,QuLogic/meson,QuLogic/meson,QuLogic/meson,QuLogic/meson,jpakkane/meson,MathieuDuponchelle/meson,pexip/meson,mesonbuild/meson,becm/meson,jpakkane/meson,becm/meson,mesonbuild/meson,becm/meson,pexip/meson,MathieuDuponchelle/meson,becm/meson,mesonbuild/meson,MathieuDuponchelle/meson,becm/meson,mesonbuild/meson,mesonbuild/meson,QuLogic/meson,jpakkane/meson,becm/meson,jpakkane/meson,QuLogic/meson,jpakkane/meson,MathieuDuponchelle/meson,pexip/meson,mesonbuild/meson,QuLogic/meson,QuLogic/meson,mesonbuild/meson,becm/meson,jpakkane/meson,QuLogic/meson,MathieuDuponchelle/meson