sort_symfile: don't overwrite the symfile with an intermediate file

tools/sort_symfile.sh

@@ -1,4 +1,5 @@
 #!/bin/sh
+TEMP_FILE=$(mktemp)
 sed \
     -e "s/^..:[0-3]/0_ROM0@&/g" \
     -e "s/^..:[4-7]/1_ROMX@&/g" \
@@ -7,6 +8,6 @@ sed \
     -e "s/^00:[C-D]/4_WRAM0@&/g" \
     -e "s/^..:[D-D]/5_WRAMX@&/g" \
     $1 \
-| sort -o $1
-TEMP_FILE=$(mktemp)
-sed -e "s/^.*@//g" $1 > $TEMP_FILE && mv $TEMP_FILE $1
+| sort -o $TEMP_FILE
+sed -e "s/^.*@//g" $TEMP_FILE > $1
+rm $TEMP_FILE