Stop adding link-native-libraries flag by default in Emscripten platform in latest Rust (#2991)

The problem with rust trying to link libc was fixed in
rust-lang/libc#4002, and this flag is not needed
anymore for recent rust versions.

Always adding this flag is preventing from using the stable Rust
toolchain as `-Z` flag can only be used with the nightly toolchains.
From Rust 1.93.0, it is possible to use stable toolchain to build to
Emscripten target, so this PR removes this flag for Rust >= 1.93.0

cc: @hoodmane

Author: ryanking13

src/compile.rs

@@ -1,6 +1,6 @@
 #[cfg(feature = "zig")]
 use crate::PlatformTag;
-use crate::target::RUST_1_64_0;
+use crate::target::{RUST_1_64_0, RUST_1_93_0};
 use crate::{BridgeModel, BuildContext, PythonInterpreter, Target};
 use anyhow::{Context, Result, anyhow, bail};
 use cargo_metadata::CrateType;
@@ -245,13 +245,18 @@ fn cargo_build_command(
             cargo_rustc.args.extend(mac_args);
         }
     } else if target.is_emscripten() {
-        // Allow user to override these default flags
-        if !rustflags
-            .flags
-            .iter()
-            .any(|f| f.contains("link-native-libraries"))
+        // The -Z link-native-libraries=no flag is needed for older Rust versions
+        // where Emscripten builds fail without it due to the behavior that it links
+        // libc automatically.
+        // From Rust 1.93.0, it is possible to build Emscripten with stable toolchain
+        // and this flag can be and should be removed.
+        if target.rustc_version.semver < RUST_1_93_0
+            && !rustflags
+                .flags
+                .iter()
+                .any(|f| f.contains("link-native-libraries"))
         {
-            debug!("Setting `-Z link-native-libraries=no` for Emscripten");
+            debug!("Setting `-Z link-native-libraries=no` for Emscripten (rust < 1.93.0)");
             rustflags.push("-Z");
             rustflags.push("link-native-libraries=no");
         }

src/target/mod.rs

@@ -23,6 +23,7 @@ mod pypi_tags;
 pub use pypi_tags::{is_arch_supported_by_pypi, validate_wheel_filename_for_pypi};
 
 pub(crate) const RUST_1_64_0: semver::Version = semver::Version::new(1, 64, 0);
+pub(crate) const RUST_1_93_0: semver::Version = semver::Version::new(1, 93, 0);
 
 /// All supported operating system
 #[derive(Debug, Clone, Copy, Eq, PartialEq, Hash, Deserialize)]