docs: Match README installation guide with meson.rst

Sync the build and install instructions in README.rst from
meson.rst

Signed-off-by: Sai Teja Pottumuttu <[email protected]>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30294>

Author: saiteja13427

README.rst

@@ -18,11 +18,9 @@ Meson (`docs/meson.rst <https://docs.mesa3d.org/meson.html>`_):
 
 .. code-block:: sh
 
-  $ mkdir build
-  $ cd build
-  $ meson ..
-  $ sudo ninja install
-
+  $ meson setup build
+  $ ninja -C build/
+  $ sudo ninja -C build/ install
 
 Support
 -------