Force unity builds off in Flex test.

test cases/frameworks/8 flex/meson.build

diff --git a/test cases/frameworks/8 flex/meson.build b/test cases/frameworks/8 flex/meson.build
index bc84bcc..55b96dd 100644
--- a/test cases/frameworks/8 flex/meson.build
+++ b/test cases/frameworks/8 flex/meson.build
@@ -28,7 +28,9 @@
 pfiles = pgen.process('parser.y')
 
 e = executable('pgen', 'prog.c',
-lfiles, pfiles)
+    lfiles,
+    pfiles,
+    override_options: 'unity=off')
 
 test('parsertest', e,
     args: [meson.current_source_dir() / 'testfile'])