When updating a split app, copy compiled files from base.apk only.

This fixes issues with some splits failing to be recompiled if they
haven't changed, but the dex files they depend on have.

The real fix will be for frameworks to generate the new expected
classpath and check in DexFile.getDexOptNeeded. Then we can undo
this change and copy over all the compiled split files again.

Bug: 62269291
Test: cts-tradefed run singleCommand cts -d --module
CtsAppSecurityHostTestCases -t android.appsecurity.cts.SplitTests

Change-Id: Id8e6dc59b16d4f10a6c2d9d81027012204e0f26b