Touch up install_dir() documentation
Touch up install_dir() documentation

It no longer removes the target tree before copying files.

thiblahute/meson,MathieuDuponchelle/meson,ernestask/meson,MathieuDuponchelle/meson,ernestask/meson,mesonbuild/meson,becm/meson,becm/meson,MathieuDuponchelle/meson,QuLogic/meson,jpakkane/meson,pexip/meson,MathieuDuponchelle/meson,jeandet/meson,thiblahute/meson,trhd/meson,jpakkane/meson,thiblahute/meson,mesonbuild/meson,thiblahute/meson,pexip/meson,trhd/meson,pexip/meson,jpakkane/meson,jpakkane/meson,mesonbuild/meson,jpakkane/meson,mesonbuild/meson,jeandet/meson,thiblahute/meson,mesonbuild/meson,trhd/meson,MathieuDuponchelle/meson,becm/meson,mesonbuild/meson,trhd/meson,jeandet/meson,pexip/meson,QuLogic/meson,ernestask/meson,mesonbuild/meson,trhd/meson,QuLogic/meson,jpakkane/meson,ernestask/meson,QuLogic/meson,trhd/meson,ernestask/meson,ernestask/meson,jeandet/meson,trhd/meson,pexip/meson,becm/meson,jeandet/meson,becm/meson,mesonbuild/meson,MathieuDuponchelle/meson,jpakkane/meson,thiblahute/meson,mesonbuild/meson,ernestask/meson,ernestask/meson,pexip/meson,thiblahute/meson,jpakkane/meson,pexip/meson,QuLogic/meson,pexip/meson,jeandet/meson,MathieuDuponchelle/meson,becm/meson,thiblahute/meson,ernestask/meson,MathieuDuponchelle/meson,jpakkane/meson,jeandet/meson,jeandet/meson,trhd/meson,MathieuDuponchelle/meson,mesonbuild/meson,pexip/meson,pexip/meson,thiblahute/meson,trhd/meson,QuLogic/meson,jeandet/meson,becm/meson,QuLogic/meson,becm/meson,becm/meson,QuLogic/meson,becm/meson,QuLogic/meson