disassemble-aml: -o actually works

Turns out that option was borken due to weird iasl
command line handling. Fix it.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

tests/data/acpi/disassemle-aml.sh

@@ -42,11 +42,16 @@ do
         else
             extra=""
         fi
-        asl=${aml}.dsl
         if [[ "${outdir}" ]];
         then
-            asl="${outdir}"/${machine}/${asl}
+            # iasl strips an extension from prefix if there.
+            # since we have some files with . in the name, the
+            # last component gets interpreted as an extension:
+            # add another extension to work around that.
+            prefix="-p ${outdir}/${aml}.dsl"
+        else
+            prefix=""
         fi
-        iasl -d -p ${asl} ${extra} ${aml}
+        iasl ${extra} ${prefix} -d ${aml}
     done
 done