build: fix -Dtools=false build

When configuring the project, meson fails with:
tests/meson.build:107:27: ERROR: Unknown variable "util_dep"

Declare the util_dep dependency regardless if 'tools' are enabled, so
tests can be built with it.

Fixes: bdc5c8793a ("meson: allow disabling tests")
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

meson.build

@@ -61,16 +61,16 @@ version_gen_h = vcs_tag(
 subdir('libfdt')
 
 dtc_tools = []
+util_dep = declare_dependency(
+  sources: ['util.c', version_gen_h],
+  include_directories: '.',
+  dependencies: libfdt_dep
+)
+
 if get_option('tools')
   flex = find_program('flex', required: true)
   bison = find_program('bison', required: true)
 
-  util_dep = declare_dependency(
-    sources: ['util.c', version_gen_h],
-    include_directories: '.',
-    dependencies: libfdt_dep
-  )
-
   lgen = generator(
     flex,
     output: '@PLAINNAME@.lex.c',