WUtil: make use of secure_getenv if the function is available

As pointed by Coverity (#50226), the function getenv can return unreliable
data, so if a sensitive application makes uses of the function 'wgethomedir'
or 'wusergnusteppath' we'd better use the GNU function secure_getenv which
ignore environment variable when used in a known critical cases.

Signed-off-by: Christophe CURIS <christophe.curis@free.fr>

WINGs/findfile.c

@@ -46,7 +46,11 @@ char *wgethomedir()
 	if (home)
 		return home;
 
+#ifdef HAVE_SECURE_GETENV
+	tmp = secure_getenv("HOME");
+#else
 	tmp = getenv("HOME");
+#endif
 	if (tmp) {
 		home = wstrdup(tmp);
 		return home;