[gmime] Fixed unit tests to build on msvc

[Rico Tzschichholz <ricotz src gnome org>]

commit a51efd4849cf815c4fbbec1511e9710f83a3801b
Author: Jeffrey Stedfast <jestedfa microsoft com>
Date:   Fri Jun 7 09:00:28 2019 -0400

    Fixed unit tests to build on msvc

 tests/test-encodings.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/tests/test-encodings.c b/tests/test-encodings.c
index 8697edb4..22f5784d 100644
--- a/tests/test-encodings.c
+++ b/tests/test-encodings.c
@@ -361,10 +361,10 @@ test_encoder (GMimeContentEncoding encoding, GByteArray *photo, GByteArray *expe
 {
        const char *name = g_mime_content_encoding_to_string (encoding);
        GMimeStream *istream, *ostream, *filtered;
+       char *buf = g_alloca (size);
        ssize_t nread, nwritten, n;
        GMimeFilter *filter;
        GByteArray *actual;
-       char buf[size];
        char *path;
        
        testsuite_check ("%s encoding; buffer-size=%zu", name, size);
@@ -438,10 +438,10 @@ test_decoder (GMimeContentEncoding encoding, GByteArray *encoded, GByteArray *ex
 {
        const char *name = g_mime_content_encoding_to_string (encoding);
        GMimeStream *istream, *ostream, *filtered;
+       char *buf = g_alloca (size);
        ssize_t nread, nwritten, n;
        GMimeFilter *filter;
        GByteArray *actual;
-       char buf[size];
        char *path;
        
        testsuite_check ("%s decoding; buffer-size=%zu", name, size);