cargo-apk: Upgrade to cargo-subcommand 0.7.0 for [env] support

Environment variables can be set and override the process environment
through `.cargo/config.toml`'s `[env]` section:
https://doc.rust-lang.org/cargo/reference/config.html#env

These config variables have specific precedence rules with regards to
overriding the environment set in the process, and can optionally
represent paths relative to the parent of the containing `.cargo/`
folder.  The entire handling of these variables is implemented in
rust-mobile/cargo-subcommand#12 and
rust-mobile/cargo-subcommand#16 which immediately
populate the process environment with these variables when
`Subcommand::new()` is called by `cargo-apk`.

cargo-apk/Cargo.toml

@@ -12,7 +12,7 @@ repository = "https://github.com/rust-windowing/android-ndk-rs"
 
 [dependencies]
 anyhow = "1.0.38"
-cargo-subcommand = "0.5.0"
+cargo-subcommand = "0.7.0"
 dunce = "1.0.1"
 env_logger = "0.8.2"
 log = "0.4.14"