configure: Show --cpu option on the help list

Signed-off-by: NChen Wen-Ren (陳韋任) <chenwj@iis.sinica.edu.tw>
Signed-off-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>

configure

@@ -1037,6 +1037,7 @@ echo "  --fmod-lib               path to FMOD library"
 echo "  --fmod-inc               path to FMOD includes"
 echo "  --oss-lib                path to OSS library"
 echo "  --enable-uname-release=R Return R for uname -r in usermode emulation"
+echo "  --cpu=CPU                Build for host CPU [$cpu]"
 echo "  --sparc_cpu=V            Build qemu for Sparc architecture v7, v8, v8plus, v8plusa, v9"
 echo "  --disable-uuid           disable uuid support"
 echo "  --enable-uuid            enable uuid support"