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

src/bootstrap/compile.rs

@@ -1126,6 +1126,7 @@ 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;

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()));
+                    }
+                }
+            }
         }
     }
 

src/test/run-make-fulldeps/output-type-permutations/Makefile

@@ -5,7 +5,7 @@ all:
 	$(call REMOVE_RLIBS,bar)
 	$(call REMOVE_DYLIBS,bar)
 	rm $(call STATICLIB,bar)
-	rm -f $(TMPDIR)/bar.{dll.exp,dll.lib,pdb}
+	rm -f $(TMPDIR)/{lib,}bar.{dll.exp,dll.lib,pdb,dll.a}
 	# Check that $(TMPDIR) is empty.
 	[ "$$(ls -1 $(TMPDIR) | wc -l)" -eq "0" ]
 
@@ -78,8 +78,8 @@ all:
 	rm $(TMPDIR)/$(call BIN,foo)
 	$(RUSTC) foo.rs --crate-type=dylib --emit=link=$(TMPDIR)/$(call BIN,foo)
 	rm $(TMPDIR)/$(call BIN,foo)
-	rm -f $(TMPDIR)/foo.{dll.exp,dll.lib,pdb}
-	[ "$$(ls -1 $(TMPDIR) | wc -l)" -eq "0" ]
+	rm -f $(TMPDIR)/{lib,}foo.{dll.exp,dll.lib,pdb,dll.a,exe.lib}
+	[ "$$(ls -1 $(TMPDIR) | wc -l)" -eq "0" ] || (ls -1 $(TMPDIR) && exit 1)
 
 	$(RUSTC) foo.rs --crate-type=staticlib -o $(TMPDIR)/foo
 	rm $(TMPDIR)/foo