linux-user: Fix undefined HOST_LONG_SIZE on PPC hosts

On my PPC host, HOST_LONG_SIZE is not defined even after
running configure. Use the normal C way of determining the
long size instead.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: malc <av1474@comtv.ru>

thunk.h

diff --git a/thunk.h b/thunk.h
index 5be8f91..87025c3 100644
--- a/thunk.h
+++ b/thunk.h
@@ -113,7 +113,7 @@
       defined(HOST_PARISC) || defined(HOST_SPARC64)
             return 4;
 #elif defined(HOST_PPC)
-            return HOST_LONG_SIZE;
+            return sizeof(void *);
 #else
             return 2;
 #endif