build script was missing platform-specific deps

[dae]

Prior to #212 being merged, the following in Cargo.toml was included the resulting BUILD file:

[target.'cfg(target_env = "msvc")'.build-dependencies]
vcpkg = { version = "0.2", optional = true }

This patch makes it work again, gated with a platform check, eg:

cargo_build_script(
    name = "libsqlite3_sys_build_script",
    srcs = glob(["**/*.rs"]),
    crate_root = "build.rs",
    edition = "2018",
    deps = [
        "@raze__cc__1_0_61//:cc",
        "@raze__pkg_config__0_3_18//:pkg_config",
    ] + selects.with_or({
        # cfg(target_env = "msvc")
        (
            "@io_bazel_rules_rust//rust/platform:i686-pc-windows-msvc",
            "@io_bazel_rules_rust//rust/platform:x86_64-pc-windows-msvc",
        ): [
            "@raze__vcpkg__0_2_10//:vcpkg",
        ],
        "//conditions:default": [],
    }),

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[dae]

@googlebot I signed it!

[google-cla]

Thanks for your pull request. It looks like this may be your first contribution to a Google open source project (if not, look below for help). Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

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Once you've signed (or fixed any issues), please reply here with @googlebot I signed it! and we'll verify it.

---

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Individual signers

• It's possible we don't have your GitHub username or you're using a different email address on your commit. Check your existing CLA data and verify that your email is set on your git commits.

Corporate signers

• Your company has a Point of Contact who decides which employees are authorized to participate. Ask your POC to be added to the group of authorized contributors. If you don't know who your Point of Contact is, direct the Google project maintainer to go/cla#troubleshoot (Public version).
• The email used to register you as an authorized contributor must be the email used for the Git commit. Check your existing CLA data and verify that your email is set on your git commits.
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[dae]

@googlebot I signed it!

[acmcarther]

Generally LGTM, though I'd like a second opinion from @UebelAndre on this if available.

[UebelAndre]

This does appear to be a regression so this LGTM! Thanks for fixing that 😄 🙏

[UebelAndre]

LGTM! Thanks for updating the PR 😄

[UebelAndre]

@acmcarther will have to do final sign off though

[dae]

The trailing comma was missing in the targeted deps case; I've moved it outside the endif to fix this.

[acmcarther]

LGTM! Thanks for putting this together!