main: Enable rdtsc support on NetBSD

Enable the Linux rdtsc implementation on NetBSD as well.  The assembly
works correctly there.

ASTERISK-29851

Change-Id: I460ad9b4d971913420ecb84186f5ba5ab03f6f37

main/asterisk.c

@@ -810,10 +810,10 @@ int64_t ast_profile(int i, int64_t delta)
 /* The RDTSC instruction was introduced on the Pentium processor and is not
  * implemented on certain clones, like the Cyrix 586. Hence, the previous
  * expectation of __i386__ was in error. */
-#if defined ( __i686__) && (defined(__FreeBSD__) || defined(linux))
+#if defined ( __i686__) && (defined(__FreeBSD__) || defined(__NetBSD__) || defined(linux))
 #if defined(__FreeBSD__)
 #include <machine/cpufunc.h>
-#elif defined(linux)
+#elif defined(__NetBSD__) || defined(linux)
 static __inline uint64_t
 rdtsc(void)
 {