Fix build-break when compiling -O0 / TAG=vpp_debug
Without inlining [TAG=vpp_debug], gcc7 (at least) refuses to produce
the indicated vector unit instruction.
@@ -616,7 +616,7 @@ u8x16_shuffle (u8x16 v, u8x16 m)
static_always_inline u32x4
u32x4_shuffle (u32x4 v, const int a, const int b, const int c, const int d)
{
-#ifdef __clang__
+#if defined(__clang__) || CLIB_DEBUG > 0
u32x4 r = { v[a], v[b], v[c], v[d] };
return r;
#else
