Revert "meson: remove one more instance of install_dir:bindir"

This reverts commit 5ffa2eaa54.

It seems that if install_dir is not specified, meson decides install path
based on file type, and non-executable binary files are installed under
/usr/share.

kernel-install is a script. So, we need to set install_dir argument
explicitly.

Fixes #18754.

src/kernel-install/meson.build

@@ -4,7 +4,8 @@ want_kernel_install = get_option('kernel-install')
 
 if want_kernel_install
         install_data('kernel-install',
-                     install_mode : 'rwxr-xr-x')
+                     install_mode : 'rwxr-xr-x',
+                     install_dir : bindir)
 
         install_data('00-entry-directory.install',
                      '50-depmod.install',