Duplicate symbols compiling libpyembed on the starter config

From a new install of PyOxidizer, gcc v7.5 on a ubuntu host:
```
cargo install pyoxidizer
pyoxidizer init-config-file torch
cd torch
pyoxidizer run
```

Produces error messages like:
```
= note: ld: error: duplicate symbol: ffi_type_double
>>> defined at types.c
>>> types.o:(ffi_type_double) in archive /tmp/pyoxidizer.1OHhrEBicQgz/build/target/x86_64-unknown-linux-gnu/debug/deps/libpyembed-cd26feed010f04a2.rlib
>>> defined at cfield.c:1652 (./Modules/_ctypes/cfield.c:1652)
>>> cfield.o:(.data+0x750) in archive /tmp/pyoxidizer.1OHhrEBicQgz/build/target/x86_64-unknown-linux-gnu/debug/deps/libpyembed-cd26feed010f04a2.rlib
```

Full output: https://gist.github.com/c7ef834a12fb1205e9413bcca4d97d62

Please let me know if any additional info would be useful for debugging.

Reproduce the failure from a new PyOxidizer install with `cargo install pyoxidizer`, `pyoxidizer init-config-file torch`, and `pyoxidizer run` on Ubuntu. Start by tracing how the starter configuration builds and links `libpyembed`, using the duplicate-symbol output and linked full log; done means the starter configuration builds without duplicate-symbol linker errors.

Written by the indexing model from the issue text.