Pass correct --image argument to oatdump.

This was broken after CL:
  Ida40dfae8c83bf7c2e737d5c7ea418e1197ad826
..which split boot image into primary and extension.
The argument to oatdump was not updated properly.

The old form before the split was:

  --image=out/soong/generic_x86/dex_bootjars/system/framework/boot.art

The new form after the split is:

  --image=out/soong/generic_x86/dex_artjars/apex/com.android.art/javalib/boot.art:out/soong/generic_x86/dex_bootjars/system/framework/boot-framework.art

Test: lunch aosp_x86-userdebug && m dump-oat

Test: Manually inspect build command to make sure correct image
  location is used:

  $ fgrep -e 'oatdump' $ANDROID_BUILD_TOP/out/soong/build.ninja | egrep -e '--image[^ ]*' -o
  --image=out/soong/generic_x86/dex_artjars/apex/com.android.art/javalib/boot.art:out/soong/generic_x86/dex_bootjars/system/framework/boot-framework.art

Change-Id: I54a5146c404aefb6eaeadbe3e9363db935ecad86
diff --git a/java/dexpreopt_bootjars.go b/java/dexpreopt_bootjars.go
index 280ce8c..88e3bc2 100644
--- a/java/dexpreopt_bootjars.go
+++ b/java/dexpreopt_bootjars.go
@@ -547,7 +547,7 @@
 			BuiltTool(ctx, "oatdumpd").
 			FlagWithInputList("--runtime-arg -Xbootclasspath:", image.dexPathsDeps.Paths(), ":").
 			FlagWithList("--runtime-arg -Xbootclasspath-locations:", image.dexLocationsDeps, ":").
-			FlagWithArg("--image=", dexpreopt.PathToLocation(image.images[arch], arch)).Implicit(image.images[arch]).
+			FlagWithArg("--image=", strings.Join(image.imageLocations, ":")).Implicits(image.imagesDeps[arch].Paths()).
 			FlagWithOutput("--output=", output).
 			FlagWithArg("--instruction-set=", arch.String())
 		rule.Build(pctx, ctx, "dump-oat-boot-"+arch.String(), "dump oat boot "+arch.String())