tests/meson: Support unit-tests non depending on virtual driver

Since tests depending on the fake device don't depend on virtual-image
driver anymore, let's change the way we organize the things, by putting
everything in the test lib, but enabling unit-tests depending on what they
depend on.

tests/meson.build

@@ -48,7 +48,6 @@ if get_option('introspection')
     endforeach
 endif
 
-if 'virtual_image' in drivers
 test_utils = static_library('fprint-test-utils',
     sources: [
         'test-utils.c',
@@ -57,10 +56,14 @@ if 'virtual_image' in drivers
     dependencies: libfprint_private_dep,
     install: false)
 
-    unit_tests = [
+unit_tests = []
+
+if 'virtual_image' in drivers
+    unit_tests += [
         'fp-context',
         'fp-device',
     ]
+endif
 
 foreach test_name: unit_tests
     basename = 'test-' + test_name
@@ -68,7 +71,8 @@ if 'virtual_image' in drivers
         sources: basename + '.c',
         dependencies: libfprint_private_dep,
         c_args: common_cflags,
-            link_with: test_utils)
+        link_with: test_utils,
+    )
     test(test_name,
         find_program('test-runner.sh'),
         suite: ['unit-tests'],
@@ -76,7 +80,6 @@ if 'virtual_image' in drivers
         env: envs,
     )
 endforeach
-endif
 
 gdb = find_program('gdb', required: false)
 if gdb.found()