[gnome-terminal] build: Fix compilation with Clang

[Egmont Koblinger <egmontkob src gnome org>]

commit 890541449d22c485c1cdf55ea571eb4225c0c197
Author: Egmont Koblinger <egmont gmail com>
Date:   Sun Dec 17 12:31:22 2017 +0100

    build: Fix compilation with Clang
    
    https://bugzilla.gnome.org/show_bug.cgi?id=790318

 src/terminal-options.c |   11 ++++++-----
 1 files changed, 6 insertions(+), 5 deletions(-)
---
diff --git a/src/terminal-options.c b/src/terminal-options.c
index 780d108..c5dcc5b 100644
--- a/src/terminal-options.c
+++ b/src/terminal-options.c
@@ -41,10 +41,11 @@
 
 static int verbosity = 1;
 
-static char * G_GNUC_FORMAT (1)
-format_as_comment (const char *format)
+/* @freeme is a workaround for Clang; see gnome-terminal bug 790318. */
+static char * G_GNUC_FORMAT (2)
+format_as_comment (char** freeme, const char *format)
 {
-  return g_strdup_printf ("# %s", format);
+  return *freeme = g_strdup_printf ("# %s", format);
 }
 
 void
@@ -56,10 +57,10 @@ terminal_fprintf (FILE* fp,
         if (verbosity < verbosity_level)
                 return;
 
-        gs_free char *commented_format = format_as_comment (format);
+        gs_free char* freeme;
         va_list args;
         va_start(args, format);
-        g_vfprintf(fp, commented_format, args);
+        g_vfprintf(fp, format_as_comment(&freeme, format), args);
         va_end(args);
 }