meson: Replace empty-string linker flags with an empty array

Meson on macOS complains about the empty string:

meson.build:556: DEPRECATION: Project uses feature that was always broken, and is now deprecated since '1.10.1': Using '' as an empty value in link_args. Replace an empty string with an empty array: `link_args : ''` -> `link_args : []`

So we do as asked.

Change-Id: Ifbdef4642c2649ee71b11b9702c43f92521b20e8
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.sourcearcade.org/c/flashprog/+/570
diff --git a/meson.build b/meson.build
index 2b40d52..9a6a586 100644
--- a/meson.build
+++ b/meson.build
@@ -576,7 +576,7 @@
 
 mapfile = 'libflashprog.map'
 if host_machine.system() == 'darwin'
-  vflag = ''
+  vflag = []
 else
   vflag = '-Wl,--version-script,@0@/@1@'.format(meson.current_source_dir(), mapfile)
 endif