meson: Don't turn string into a list in nativesdk

In the current version of meson, some path variables only
accept a string not a list.

(From OE-Core rev: 68f20ac5524a5db8a09a90df796b4862cf747d3c)

Signed-off-by: Randy Li <ayaka@soulik.info>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-devtools/meson/meson/meson-setup.py

@@ -10,9 +10,13 @@ class Template(string.Template):
 class Environ():
     def __getitem__(self, name):
         val = os.environ[name]
-        val = ["'%s'" % x for x in val.split()]
-        val = ', '.join(val)
-        val = '[%s]' % val
+        val = val.split()
+        if len(val) > 1:
+            val = ["'%s'" % x for x in val]
+            val = ', '.join(val)
+            val = '[%s]' % val
+        elif val:
+            val = "'%s'" % val.pop()
         return val
 
 try: