[babl] tests: use putenv when setting env vars, for win32 compatibility

[Øyvind "pippin" Kolås <ok src gnome org>]

commit fc4f17ff3cb750d714188b6f063e28bd55ba0ee1
Author: Øyvind Kolås <pippin gimp org>
Date:   Thu May 28 14:07:20 2020 +0200

    tests: use putenv when setting env vars, for win32 compatibility

 tests/conversions.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/tests/conversions.c b/tests/conversions.c
index 3074c4fd7..9503d041d 100644
--- a/tests/conversions.c
+++ b/tests/conversions.c
@@ -58,7 +58,8 @@ int
 main (int    argc,
       char **argv)
 {
-  setenv ("BABL_DEBUG_MISSING", "1", 1);
+  putenv ("BABL_DEBUG_CONVERSIONS" "=" "1");
+  putenv ("BABL_DEBUG_MISSING" "=" "1");
   babl_init ();
   
   for (int i = 0; i < sizeof (fishes)/sizeof(fishes[0]);i ++)