asm code seems to broken/not implemented on amd64 in general; at least fixes build on amd64-debian4.0, too

imagemagick/imagemagick.spec

@@ -103,7 +103,7 @@ AutoReqProv:  no
 %build
     cppflags=""
     case "%{l_platform -t}" in
-        amd64-freebsd* ) cppflags="-DPNG_NO_ASSEMBLER_CODE" ;;
+        amd64-* ) cppflags="-DPNG_NO_ASSEMBLER_CODE" ;;
     esac
     CC="%{l_cc}" \
     CXX="%{l_cxx}" \