Update how WASI toolchains are used in CI and bootstrap

This commit updates how the WASI targets are configured with their
toolchain. Long ago a `config.toml` option of `wasi-root` was added to
enable building with the WASI files produced by wasi-libc. Additionally
for CI testing and release building the Rust toolchain has been using a
hard-coded commit of wasi-libc which is bundled with the release of the
`wasm32-wasip1` target, for example.

Nowadays though the wasi-sdk project, the C/C++ toolchain for WASI, is
the go-to solution for compiling/linking WASI code and contains the
more-or-less official releases of wasi-libc. This commit migrates CI to
using wasi-sdk releases and additionally updates `bootstrap` to
recognize when this is configured. This means that with `$WASI_SDK_PATH`
configured there's no further configuration necessary to get a working
build. Notably this also works better for the new targets of WASI as
well, such as `wasm32-wasip2` and `wasm32-wasip1-threads` where the
wasi-sdk release now has libraries for all targets bundled within it.

3 files changed, 38 insertions, 20 deletions

diff --git a/src/bootstrap/src/core/build_steps/compile.rs b/src/bootstrap/src/core/build_steps/compile.rs
index 9420e40d6c2..50149d370d5 100644
--- a/src/bootstrap/src/core/build_steps/compile.rs
+++ b/src/bootstrap/src/core/build_steps/compile.rs
@@ -394,16 +394,13 @@ fn copy_self_contained_objects(
             target_deps.push((libunwind_path, DependencyType::TargetSelfContained));
         }
     } else if target.contains("-wasi") {
-        let srcdir = builder
-            .wasi_root(target)
-            .unwrap_or_else(|| {
-                panic!(
-                    "Target {:?} does not have a \"wasi-root\" key in Config.toml",
-                    target.triple
-                )
-            })
-            .join("lib")
-            .join(target.to_string().replace("-preview1", "").replace("p2", "").replace("p1", ""));
+        let srcdir = builder.wasi_libdir(target).unwrap_or_else(|| {
+            panic!(
+                "Target {:?} does not have a \"wasi-root\" key in Config.toml \
+                    or `$WASI_SDK_PATH` set",
+                target.triple
+            )
+        });
         for &obj in &["libc.a", "crt1-command.o", "crt1-reactor.o"] {
             copy_and_stamp(
                 builder,
@@ -514,12 +511,8 @@ pub fn std_cargo(builder: &Builder<'_>, target: TargetSelection, stage: u32, car
         }
 
         if target.contains("-wasi") {
-            if let Some(p) = builder.wasi_root(target) {
-                let root = format!(
-                    "native={}/lib/{}",
-                    p.to_str().unwrap(),
-                    target.to_string().replace("-preview1", "")
-                );
+            if let Some(dir) = builder.wasi_libdir(target) {
+                let root = format!("native={}", dir.to_str().unwrap());
                 cargo.rustflag("-L").rustflag(&root);
             }
         }
diff --git a/src/bootstrap/src/lib.rs b/src/bootstrap/src/lib.rs
index 1a8322c0dfd..027bcac045c 100644
--- a/src/bootstrap/src/lib.rs
+++ b/src/bootstrap/src/lib.rs
@@ -1351,9 +1351,24 @@ impl Build {
         self.musl_root(target).map(|root| root.join("lib"))
     }
 
-    /// Returns the sysroot for the wasi target, if defined
-    fn wasi_root(&self, target: TargetSelection) -> Option<&Path> {
-        self.config.target_config.get(&target).and_then(|t| t.wasi_root.as_ref()).map(|p| &**p)
+    /// Returns the `lib` directory for the WASI target specified, if
+    /// configured.
+    ///
+    /// This first consults `wasi-root` as configured in per-target
+    /// configuration, and failing that it assumes that `$WASI_SDK_PATH` is
+    /// set in the environment, and failing that `None` is returned.
+    fn wasi_libdir(&self, target: TargetSelection) -> Option<PathBuf> {
+        let configured =
+            self.config.target_config.get(&target).and_then(|t| t.wasi_root.as_ref()).map(|p| &**p);
+        if let Some(path) = configured {
+            return Some(path.join("lib").join(target.to_string()));
+        }
+        let mut env_root = PathBuf::from(std::env::var_os("WASI_SDK_PATH")?);
+        env_root.push("share");
+        env_root.push("wasi-sysroot");
+        env_root.push("lib");
+        env_root.push(target.to_string());
+        Some(env_root)
     }
 
     /// Returns `true` if this is a no-std `target`, if defined
diff --git a/src/bootstrap/src/utils/cc_detect.rs b/src/bootstrap/src/utils/cc_detect.rs
index 3ba4e0cb686..7e59b7f6f57 100644
--- a/src/bootstrap/src/utils/cc_detect.rs
+++ b/src/bootstrap/src/utils/cc_detect.rs
@@ -47,7 +47,7 @@ fn cc2ar(cc: &Path, target: TargetSelection) -> Option<PathBuf> {
         Some(PathBuf::from("ar"))
     } else if target.contains("vxworks") {
         Some(PathBuf::from("wr-ar"))
-    } else if target.contains("android") {
+    } else if target.contains("android") || target.contains("-wasi") {
         Some(cc.parent().unwrap().join(PathBuf::from("llvm-ar")))
     } else {
         let parent = cc.parent().unwrap();
@@ -223,6 +223,16 @@ fn default_compiler(
             }
         }
 
+        t if t.contains("-wasi") => {
+            let root = PathBuf::from(std::env::var_os("WASI_SDK_PATH")?);
+            let compiler = match compiler {
+                Language::C => format!("{t}-clang"),
+                Language::CPlusPlus => format!("{t}-clang++"),
+            };
+            let compiler = root.join("bin").join(compiler);
+            Some(compiler)
+        }
+
         _ => None,
     }
 }