link with $CC if there's no C++

lib/CompileStep.h

 	toolchain::FileType type_;
 
 	bool checkHasChanged(const std::string &outDir) override;
+	toolchain::FileType doGetLinkType() override { return type_; }
 	void doBuild(const std::string &outDir) override;
 	void doWriteCompDB(const std::string &outDir, compdb::Writer &w) override;
 	std::vector<std::string> getPublicLDFlags(const std::string &outDir) override;

lib/DepNode.h

 #include <condition_variable>
 
 #include "compdb.h"
+#include "toolchain.h"
 
 class DepNode {
 public:
 	virtual ~DepNode() = default;
 
 	const std::vector<std::shared_ptr<DepNode>> &children() { return deps_; }
+	toolchain::FileType linkType() { return doGetLinkType(); }
 	void addChild(std::shared_ptr<DepNode> node);
 	bool hasChanged(const std::string &outDir);
 	void startBuild(const std::string &outDir);
 	void joinBuild();
 	void writeCompDB(const std::string &outDir, compdb::Writer &w);
+
 	virtual std::vector<std::string> publicLDFlags(const std::string &outDir);
 	virtual std::vector<std::string> publicLDLibs(const std::string &outDir);
 	virtual std::vector<std::string> publicObjects(const std::string &outDir);
 	};
 
 	virtual bool checkHasChanged(const std::string &outDir) = 0;
+	virtual toolchain::FileType doGetLinkType() = 0;
 	virtual void doBuild(const std::string &outDir) = 0;
 	virtual void doWriteCompDB(const std::string &outDir, compdb::Writer &w) {}
 	virtual std::vector<std::string> getPublicLDFlags(const std::string &outDir) { return {}; }

lib/LinkStep.cc

 	sys::execute(command, conf);
 }
 
+toolchain::FileType LinkStep::doGetLinkType() {
+	for (auto &child: children()) {
+		if (child->linkType() == toolchain::FileType::CXX) {
+			return toolchain::FileType::CXX;
+		}
+	}
+
+	return toolchain::FileType::C;
+}
+
 std::vector<std::string> &LinkStep::linkCommand(const std::string &outDir) {
 	if (hasLinkCommand_) {
 		return linkCommand_;
 	// TODO: Don't use FileType::CXX hard-coded here
 	linkCommand_ = toolchain::getLinkCommand(
 			publicLDFlags(outDir), publicLDLibs(outDir),
-			toolchain::FileType::CXX, type_, objs, path_, outDir);
+			linkType(), type_, objs, path_, outDir);
 	hasLinkCommand_ = true;
 	return linkCommand_;
 }

lib/LinkStep.h

 	toolchain::TargetType type_;
 
 	bool checkHasChanged(const std::string &outDir) override;
+	toolchain::FileType doGetLinkType() override;
 	void doBuild(const std::string &outDir) override;
 
 	bool hasLinkCommand_ = false;