Keep the symbol table in the shared libraries.

In order to allow the unwinder code to have meaningful names for
art functions, leave the symbol table.

Here are the size increases:

Platform    Size Increase
--------    -------------
arm         ~631K
arm64       ~631K
mips        ~424K
x86         ~565K
x86_64      ~565K

Bug: 12958251
Change-Id: Ib8bf11bef648f8296f4d6544f7b2af0d7f969ad8