Use cargo-ndk as a _LINKER wrapper to pass --target to Clang

This is an alternative workaround for #92 that's similar to the solution
used in ndk-build except that the `--target=<triple><api-level>` argument
for Clang is injected by using cargo-ndk as a linker wrapper instead of
trying to modify CARGO_ENCODED_RUSTFLAGS.

It turned out to be practically impossible to be able to reliably
set CARGO_ENCODED_RUSTFLAGS without risking trampling over rustflags
that might be configured via Cargo (for example `target.<cfg>.rustflags`
are especially difficult to read outside of cargo itself)

This approach avoids hitting the command line length limitations of the
current workaround and avoids needing temporary hard links or copying
the cargo-ndk binary to the target/ directory.

Even though we've only seen quoting issues with the Windows `.cmd`
wrappers this change to avoid using the wrapper scripts is being
applied consistently for all platforms. E.g. considering the upstream
recommendation to avoid the wrapper scripts if possible:

https://android-review.googlesource.com/c/platform/ndk/+/2134712

Fixes: #92
Fixes: #104
Addresses: android/ndk#1856

Cargo.toml

@@ -31,7 +31,3 @@ pathos = "0.3.0"
 serde = { version = "1.0.152", features = ["derive"] }
 toml = "0.5.10"
 version_check = "0.9.4"
-
-[target.'cfg(windows)'.dependencies]
-tempfile = "3.5.0"
-wargs = "0.1.0"