run: factor out arm and aarch64

Make the generated command beautiful and perfect without any trailing whitespace.
I have to review my life choices

run

@@ -144,7 +144,7 @@ while getopts a:c:DdE:e:F:f:G:ghIiKkL:M:m:N:n:PQ:RrT:t:U:uVX:x OPT; do
   esac
 done
 shift "$(($OPTIND - 1))"
-extra_flags="$extra_flags $@"
+extra_flags="${extra_flags}${@}"
 OPTIND=1
 if [ -n "$extra_opts" ]; then
   while getopts b OPT $extra_opts; do
@@ -209,7 +209,7 @@ ${gem5opts} \
 "
   if "$gem5_fsbiglittle"; then
       cmd="${gem5_common}\
-"${common_gem5_default_src_dir}/configs/example/arm/fs_bigLITTLE.py" \
+"${common_gem5_default_src_dir}/configs/example/arm/fs_bigLITTLE.py" \\
 --big-cpus=2 \\
 --cpu-type=atomic \\
 --disk="${common_images_dir}/rootfs.ext2" \\
@@ -251,8 +251,8 @@ ${extra_flags} \
 else
   mkdir -p "$common_qemu_run_dir"
   if [ -z "$debug_vm" ]; then
-    serial_monitor='-serial mon:stdio \
+    serial_monitor="-serial mon:stdio \\
-'
+"
   else
     serial_monitor=
   fi
@@ -260,7 +260,7 @@ else
     extra_flags="${extra_flags} -enable-kvm"
   fi
   if "$kgdb"; then
-    extra_flags_qemu="$extra_flags_qemu -serial 'tcp::${common_gdb_port},server,nowait' \\
+    extra_flags_qemu="${extra_flags_qemu}-serial 'tcp::${common_gdb_port},server,nowait' \\
 "
   fi
   if "$prebuilt"; then
@@ -311,7 +311,7 @@ ${vnc}"
       extra_flags="${extra_flags}-drive 'file=${common_qcow2_file},format=qcow2,if=${driveif}${snapshot}${rrid}' \\
 "
       if [ -n "$rr" ]; then
-        extra_flags="${extra_flags} \\
+        extra_flags="${extra_flags}\
 -drive driver=blkreplay,if=none,image=img-direct,id=img-blkreplay \\
 -device ide-hd,drive=img-blkreplay \\
 "
@@ -339,40 +339,29 @@ ${qemu_common} \
 -M pc \\
 -append '${root} nopat ${extra_append}' \\
 -device edu \\
-${extra_flags} \
 "
     ;;
-    arm)
+    arm|aarch64)
       if "$kgdb"; then
         extra_append="${extra_append} kgdboc=ttyAMA0,115200"
       fi
+      if [  "$common_arch" = arm ]; then
+        cpu=cortex-a15
+      else
+        cpu=cortex-a57
+      fi
       cmd="\
 ${qemu_common}\
 -M virt \\
 -append '${root} ${extra_append}' \\
--cpu cortex-a15 \\
+-cpu "$cpu" \\
 ${virtio_gpu_pci}\
-${extra_flags} \
-"
-    ;;
-    aarch64)
-      if "$kgdb"; then
-        extra_append="${extra_append} kgdboc=ttyAMA0,115200"
-      fi
-      cmd="\
-${qemu_common} \
--M virt \\
--append '${root} ${extra_append}' \\
--cpu cortex-a57 \\
-${virtio_gpu_pci} \
-${extra_flags} \
 "
     ;;
     mips64)
       if ! "$ramfs"; then
         root='root=/dev/hda'
-        extra_flags="${extra_flags} \
+        extra_flags="${extra_flags}-drive 'file=${common_qcow2_file},format=qcow2${snapshot}' \\
--drive 'file=${common_qcow2_file},format=qcow2${snapshot}' \\
 "
       fi
       cmd="\
@@ -380,7 +369,6 @@ ${qemu_common} \
 -M malta \\
 -append '${root} ${extra_append}' \\
 -cpu I6400 \\
-${extra_flags} \
 "
     ;;
   esac
@@ -392,9 +380,11 @@ if "$tmux"; then
     eval "./tmu ./rungdb -a '${common_arch} -L ${common_linux_variant}' -n ${common_run_id} ${tmux_args}"
   fi
 fi
-cmd="time ${cmd}"
+cmd="time \\
+${cmd}"
 if [ -z "$debug_vm" ]; then
   cmd="${cmd}\
+${extra_flags}\
 |& tee >(ts -s %.s > ${common_termout_file})\
 "
 fi