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GH-38077: [C++] Output bundled GoogleTest to ${BUILD_DIR}/${CONFIG} (#38132)

### Rationale for this change

To find DLLs on Windows, we need to add a directory of these DLLs to PATH or put these DLLs to the same directory of the target .exe.

### What changes are included in this PR?

Output bundled GoogleTest's DLLs to the same directory of the test .exe.

### Are these changes tested?

Yes.

### Are there any user-facing changes?

No.
* Closes: #38077

Authored-by: Sutou Kouhei <kou@clear-code.com>
Signed-off-by: Sutou Kouhei <kou@clear-code.com>