Use "raw-dylib" for non-win7 Windows Targets

Now that we only use the standard Windows backend on Windows 1.78 or
later, we can just use `kind = "raw-dylib"` to link to
`bcryptprimitives.dll`.

This reduces the `--target=all` dependancy graph for `getrandom` to:
```
└── getrandom v0.3.1
    ├── cfg-if v1.0.0
    ├── libc v0.2.170
    ├── r-efi v5.2.0
    └── wasi v0.14.2+wasi-0.2.4
        └── wit-bindgen-rt v0.39.0
            └── bitflags v2.9.0
```

Signed-off-by: Joe Richey <joerichey@google.com>

Author: josephlr

Cargo.lock

@@ -70,10 +70,6 @@ libc = { version = "0.2.154", default-features = false }
 [target.'cfg(all(target_arch = "wasm32", target_os = "wasi", target_env = "p2"))'.dependencies]
 wasi = { version = "0.14", default-features = false }
 
-# windows7
-[target.'cfg(all(windows, not(target_vendor = "win7"), not(getrandom_windows_legacy)))'.dependencies]
-windows-targets = "0.53"
-
 # wasm_js
 [target.'cfg(all(target_arch = "wasm32", any(target_os = "unknown", target_os = "none")))'.dependencies]
 wasm-bindgen = { version = "0.2.98", default-features = false, optional = true }

Cargo.toml

@@ -40,7 +40,7 @@ fn main() {
     }
 
     // Use `RtlGenRandom` on older compiler versions since win7 targets
-    // were introduced only in Rust 1.78
+    // TODO(MSRV 1.78): Remove this check
     let target_family = env::var_os("CARGO_CFG_TARGET_FAMILY").and_then(|f| f.into_string().ok());
     if target_family.as_deref() == Some("windows") {
         /// Minor version of the Rust compiler in which win7 targets were inroduced

build.rs

@@ -26,13 +26,27 @@ use core::mem::MaybeUninit;
 pub use crate::util::{inner_u32, inner_u64};
 
 // Binding to the Windows.Win32.Security.Cryptography.ProcessPrng API. As
-// bcryptprimitives.dll lacks an import library, we use the windows-targets
-// crate to link to it.
-//
-// TODO(MSRV 1.71): Migrate to linking as raw-dylib directly.
-// https://github.com/joboet/rust/blob/5c1c72572479afe98734d5f78fa862abe662c41a/library/std/src/sys/pal/windows/c.rs#L119
-// https://github.com/microsoft/windows-rs/blob/0.60.0/crates/libs/targets/src/lib.rs
-windows_targets::link!("bcryptprimitives.dll" "system" fn ProcessPrng(pbdata: *mut u8, cbdata: usize) -> i32);
+// bcryptprimitives.dll lacks an import library, we use "raw-dylib". This
+// was added in Rust 1.65 for x86_64/aarch64 and in Rust 1.71 for x86.
+// We don't need MSRV 1.71, as we only use this backend on Rust 1.78 and later.
+#[cfg_attr(
+    target_arch = "x86",
+    link(
+        name = "bcryptprimitives",
+        kind = "raw-dylib",
+        import_name_type = "undecorated"
+    )
+)]
+#[cfg_attr(
+    not(target_arch = "x86"),
+    link(name = "bcryptprimitives", kind = "raw-dylib")
+)]
+extern "system" {
+    fn ProcessPrng(pbdata: *mut u8, cbdata: usize) -> BOOL;
+}
+#[allow(clippy::upper_case_acronyms)]
+type BOOL = core::ffi::c_int; // MSRV 1.64, similarly OK for this backend.
+const TRUE: BOOL = 1;
 
 #[inline]
 pub fn fill_inner(dest: &mut [MaybeUninit<u8>]) -> Result<(), Error> {
@@ -42,6 +56,6 @@ pub fn fill_inner(dest: &mut [MaybeUninit<u8>]) -> Result<(), Error> {
     // return 1 (which is how windows represents TRUE).
     // See the bottom of page 6 of the aforementioned Windows RNG
     // whitepaper for more information.
-    debug_assert!(result == 1);
+    debug_assert!(result == TRUE);
     Ok(())
 }