rustc: codegen: Build import library for all windows targets

So far it is assumed that using a DLL as a -l parameter argument is ok, but the assumption doesn't hold when compiling the native code with llvm. In which case, an import library is required, so let's build one This also requires the cargo counterpart to add the import library in the stamp files, at least when compiling libstd. Otherwise, the files don't get uplifted
rust-lang · Centril · May 27, 2019 · May 27, 2019 · May 27, 2019 · May 27, 2019
commit 1c6b4d546dc1a7118cc3a9e940ae98f2a342f34a
diff --git a/src/bootstrap/compile.rs b/src/bootstrap/compile.rs
@@ -1130,6 +1130,7 @@ pub fn run_cargo(builder: &Builder<'_>,
             // Skip files like executables
             if !filename.ends_with(".rlib") &&
                !filename.ends_with(".lib") &&
+               !filename.ends_with(".a") &&
                !is_dylib(&filename) &&
                !(is_check && filename.ends_with(".rmeta")) {
                 continue;

diff --git a/src/librustc_codegen_ssa/back/linker.rs b/src/librustc_codegen_ssa/back/linker.rs
@@ -368,6 +368,26 @@ impl<'a> Linker for GccLinker<'a> {
             }
         } else {
             self.cmd.arg("-shared");
+            if self.sess.target.target.options.is_like_windows {
+                // The output filename already contains `dll_suffix` so
+                // the resulting import library will have a name in the
+                // form of libfoo.dll.a
+                let implib_name = out_filename
+                    .file_name()
+                    .and_then(|file| file.to_str())
+                    .map(|file| format!("{}{}{}",
+                         self.sess.target.target.options.staticlib_prefix,
+                         file,
+                         self.sess.target.target.options.staticlib_suffix));
+                if let Some(implib_name) = implib_name {
+                    let implib = out_filename
+                        .parent()
+                        .map(|dir| dir.join(&implib_name));
+                    if let Some(implib) = implib {
+                        self.linker_arg(&format!("--out-implib,{}", (*implib).to_str().unwrap()));
+                    }
+                }
+            }
         }
     }