When configuring QEMU with --disable-system, meson keeps showing
libfdt as "auto". Mark it as disabled instead.

Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
 meson.build | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/meson.build b/meson.build
index df25e7a5e7..9460875693 100644
--- a/meson.build
+++ b/meson.build
@@ -2266,8 +2266,8 @@ if get_option('cfi') and slirp_opt == 'system'
 endif
 
 fdt = not_found
-fdt_opt = get_option('fdt')
 if have_system
+  fdt_opt = get_option('fdt')
   if fdt_opt in ['enabled', 'auto', 'system']
     have_internal = fs.exists(meson.current_source_dir() / 'dtc/libfdt/Makefile.libfdt')
     fdt = cc.find_library('fdt', kwargs: static_kwargs,
@@ -2310,6 +2310,8 @@ if have_system
     fdt = declare_dependency(link_with: libfdt,
                              include_directories: fdt_inc)
   endif
+else
+  fdt_opt = 'disabled'
 endif
 if not fdt.found() and fdt_required.length() > 0
   error('fdt not available but required by targets ' + ', '.join(fdt_required))
-- 
2.34.1