Filter duplicate sources in ART's codegen customizer.

With this change, it is now possible to write the following in ART
Blueprint files:

  codegen: {
      mips: {
          srcs: ["disassembler_mips.cc"],
      },
      mips64: {
          srcs: ["disassembler_mips.cc"],
      },
  },

and have it work even if the `mips` and `mips64` are both enabled.

Before this change, this construction would have been rejected with
the following error message:

  "FAILED: ninja: […]: multiple rules generate […]disassembler_mips.o"

Test: m test-art-host
Bug: 119090273
Change-Id: I0a20a65ce7ab308644f3018a89fa96e5bdcdbdc4
1 file changed