Add metadata for cargo bininstall

[vmiklos]

In contrast with the default documented at
https://github.com/ryankurte/cargo-binstall#supporting-binary-installation:

• our pkg-url doesn't contain a version
• bin-dir is just the executable without a parent directory
• pkg-fmt is tar.gz, not tgz

Fixes #168.

[taiki-e]

Thanks!

bors r+

[bors]

Build succeeded:

• ci

[taiki-e]

hmm

$ cargo binstall cargo-llvm-cov
13:38:51 [INFO] Installing package: 'cargo-llvm-cov'
Error: unknown variant `tar.gz`, expected one of `tar`, `tgz`, `txz`, `zip`, `bin` for key `package.metadata.binstall.pkg-fmt` at line 121 column 1

Caused by:
    unknown variant `tar.gz`, expected one of `tar`, `tgz`, `txz`, `zip`, `bin` for key `package.metadata.binstall.pkg-fmt` at line 121 column 1

UPDATE: filed #176

[taiki-e]

Confirmed cargo binstall cargo-llvm-cov works for 0.4.3 (#176).

$ cargo binstall cargo-llvm-cov
14:11:15 [INFO] Installing package: 'cargo-llvm-cov'
14:11:18 [INFO] Checking for package at: 'https://github.com/taiki-e/cargo-llvm-cov/releases/download/v0.4.3/cargo-llvm-cov-x86_64-apple-darwin.tar.gz'
14:11:19 [INFO] The package will be downloaded from github.com
14:11:19 [INFO] Downloading package from: 'https://github.com/taiki-e/cargo-llvm-cov/releases/download/v0.4.3/cargo-llvm-cov-x86_64-apple-darwin.tar.gz'
14:11:19 [INFO] This will install the following binaries:
14:11:19 [INFO]   - cargo-llvm-cov (cargo-llvm-cov -> /Users/taiki/.cargo/bin/cargo-llvm-cov-v0.4.3)
14:11:19 [INFO] And create (or update) the following symlinks:
14:11:19 [INFO]   - cargo-llvm-cov (/Users/taiki/.cargo/bin/cargo-llvm-cov -> cargo-llvm-cov-v0.4.3)
14:11:19 [INFO] Do you wish to continue? yes/no
yes
14:11:22 [INFO] Installing binaries...
14:11:22 [INFO] Installation complete!

[vmiklos]

Thanks! :-) Sorry, the metadata looked almost trivial, I assumed that one can only test this for real with a released version (using the cargo binstall --version <version> <name> syntax), so it seemed fair to submit a blind PR. I should have stated in the description that this is a blind metadata. Glad to hear you could fix it up.