Fails to build when patching from git

I'm having trouble building from a patch when the source is git. The patching works fine when the patch is defined as a path. I first thought it was my forked repo that was causing the error, but even patching from this repo causes the same error.

```
[dependencies]
openssl = { version = "0.10.62", features = ["vendored"] }

[patch.crates-io]
openssl-src = { git = "https://github.com/alexcrichton/openssl-src-rs.git", tag = "300.2.1+3.2.0" }
```

```
error: failed to run custom build command for `openssl-sys v0.9.98`

Caused by:
process didn't exit successfully: `/Users/dangross/Source/Projects/breez-sdk/libs/sdk-wasm/target/release/build/openssl-sys-9b34fa47009423a2/build-script-main` (exit status: 101)
--- stdout
cargo:rerun-if-env-changed=WASM32_WASMER_WASI_OPENSSL_NO_VENDOR
WASM32_WASMER_WASI_OPENSSL_NO_VENDOR unset
cargo:rerun-if-env-changed=OPENSSL_NO_VENDOR
OPENSSL_NO_VENDOR unset

--- stderr
thread 'main' panicked at /Users/dangross/.cargo/git/checkouts/openssl-src-rs-2e32af6c1ebd97b1/47d047a/src/lib.rs:644:35:
called `Result::unwrap()` on an `Err` value: Error { kind: InvalidInput, message: "the source path is neither a regular file nor a symlink to a regular file" }
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
warning: build failed, waiting for other jobs to finish...
```

It is failing on this line: https://github.com/alexcrichton/openssl-src-rs/blob/47d047ae37ed3489dad7164e1732cbeac689d185/src/lib.rs#L644

```
Error { kind: InvalidInput, message: "the source path is neither a regular file nor a symlink to a regular file" }
```

when copying `openssl/cloudflare-quiche/fuzz/mayhem/qpack_decode/corpus` which is a symlink to the `openssl/cloudflare-quiche/fuzz/corpus/qpack_decode` directory.