Tweak wasm_base target spec to indicate linker is not GNU and update linker inferring logic for wasm-ld.

Author: luqmana

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -1005,6 +1005,8 @@ fn linker_and_flavor(sess: &Session) -> (PathBuf, LinkerFlavor) {
                     || stem.ends_with("-clang")
                 {
                     LinkerFlavor::Gcc
+                } else if stem == "wasm-ld" || stem.ends_with("-wasm-ld") {
+                    LinkerFlavor::Lld(LldFlavor::Wasm)
                 } else if stem == "ld" || stem == "ld.lld" || stem.ends_with("-ld") {
                     LinkerFlavor::Ld
                 } else if stem == "link" || stem == "lld-link" {

compiler/rustc_codegen_ssa/src/back/linker.rs

@@ -472,21 +472,23 @@ impl<'a> Linker for GccLinker<'a> {
         // eliminate the metadata. If we're building an executable, however,
         // --gc-sections drops the size of hello world from 1.8MB to 597K, a 67%
         // reduction.
-        } else if self.sess.target.linker_is_gnu && !keep_metadata {
+        } else if (self.sess.target.linker_is_gnu || self.sess.target.is_like_wasm)
+            && !keep_metadata
+        {
             self.linker_arg("--gc-sections");
         }
     }
 
     fn no_gc_sections(&mut self) {
         if self.sess.target.is_like_osx {
             self.linker_arg("-no_dead_strip");
-        } else if self.sess.target.linker_is_gnu {
+        } else if self.sess.target.linker_is_gnu || self.sess.target.is_like_wasm {
             self.linker_arg("--no-gc-sections");
         }
     }
 
     fn optimize(&mut self) {
-        if !self.sess.target.linker_is_gnu {
+        if !self.sess.target.linker_is_gnu && !self.sess.target.is_like_wasm {
             return;
         }
 

compiler/rustc_target/src/spec/wasm_base.rs

@@ -102,6 +102,7 @@ pub fn options() -> TargetOptions {
         // we use the LLD shipped with the Rust toolchain by default
         linker: Some("rust-lld".to_owned()),
         lld_flavor: LldFlavor::Wasm,
+        linker_is_gnu: false,
 
         // No need for indirection here, simd types can always be passed by
         // value as the whole module either has simd or not, which is different