Skip luajit subproject when installing

After switching to the upstream luajit wrap, luajit is now
installed by default.
Most other wrapdb subprojects will also be installed by default,
but for those it is not always clear whether they should be skipped.

Fixes #321.

README.md

@@ -105,7 +105,7 @@ sudo apt install build-essential pkg-config meson ninja-build gettext intltool l
 ``` bash
 meson setup build --prefix=/usr/local --buildtype=release --strip -Dsystem_luajit=false
 meson compile -C build
-meson install -C build
+meson install -C build --skip-subprojects luajit
 ```
 
 ## Updating Moonscript

tools/osx-bundle.sh

@@ -53,7 +53,7 @@ echo
 echo "---- Installing files ----"
 CURRENT_DIR=`pwd`
 cd ${BUILD_DIR}
-ninja install
+meson install --skip-subprojects luajit
 cd ${CURRENT_DIR}
 
 echo