Remove the size of oatexec and oatdex dynamic symobls.

We use only the address of them so the size is irrelevant.

The current size covers the whole section, which collides
with all other symbols which really confuses native tools.

Test: m test-art-host-gtest
Change-Id: Iad4e3f0ba5dafdf43b3f20f499725c793d35acf6