Add stub getegid impl for platforms lacking it

We already have stubs for getuid, geteuid, getgid but
not for getegid. Something in gnulib already does a
check for it during configure, so we already have the
HAVE_GETEGID macro defined.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
(cherry picked from commit c566fa1ad0)

src/util/virutil.h

@@ -108,6 +108,10 @@ static inline int geteuid (void) { return 0; }
 static inline int getgid (void) { return 0; }
 # endif
 
+# ifndef HAVE_GETEGID
+static inline int getegid (void) { return 0; }
+# endif
+
 char *virGetHostname(void);
 
 char *virGetUserDirectory(void);