Failed to build on Ubuntu 18.04 at pyembed v0.1.0

Hi,

I just cloned the repo and run "cargo build":

[...]
   Compiling git2 v0.9.1
   Compiling pyoxidizer v0.1.2 (/home/ehellou/DEVEL/PyOxidizer/pyoxidizer)
   Compiling cookie_store v0.7.0
   Compiling reqwest v0.9.18
   Compiling pyembed v0.1.0 (/home/ehellou/DEVEL/PyOxidizer/pyembed)
error: failed to run custom build command for `pyembed v0.1.0 (/home/ehellou/DEVEL/PyOxidizer/pyembed)`
process didn't exit successfully: `/home/ehellou/DEVEL/PyOxidizer/target/debug/build/pyembed-cdba5daab28bc600/build-script-build` (exit code: 101)
--- stdout
cargo:rerun-if-changed=build.rs
cargo:rerun-if-env-changed=PYOXIDIZER_CONFIG

--- stderr
thread 'main' panicked at 'Could not find PyOxidizer config file', pyoxidizer/src/pyrepackager/repackage.rs:2640:17
note: Run with `RUST_BACKTRACE=1` for a backtrace.

warning: build failed, waiting for other jobs to finish...
error: build failed
helio@xps13ubuntu:PyOxidizer$ rust
rustc     rustdoc   rust-gdb  
helio@xps13ubuntu:PyOxidizer$ rust
rustc     rustdoc   rust-gdb  
helio@xps13ubuntu:PyOxidizer$ rustc --version
rustc 1.32.0
helio@xps13ubuntu:PyOxidizer$ cargo --version
cargo 1.32.0

Reproduce the failure with cargo build using Rust 1.32.0 on Ubuntu 18.04, then inspect pyembed/build.rs and the panic location in pyoxidizer/src/pyrepackager/repackage.rs:2640. Done means identifying why the PyOxidizer config file is not found and confirming that the project builds successfully in the reported environment.