Do not record response files as dependency files

Fixes #1258

common/common.h

@@ -1025,6 +1025,9 @@ class MappedFile {
   MappedFile *parent = nullptr;
   MappedFile *thin_parent = nullptr;
 
+  // For --dependency-file
+  bool is_dependency = true;
+
 #ifdef _WIN32
   HANDLE fd = INVALID_HANDLE_VALUE;
 #else

elf/cmdline.cc

@@ -227,6 +227,8 @@ read_response_file(Context<E> &ctx, std::string_view path, i64 depth) {
   MappedFile *mf = must_open_file(ctx, std::string(path));
   std::string_view data((char *)mf->data, mf->size);
 
+  mf->is_dependency = false;
+
   while (!data.empty()) {
     if (isspace(data[0])) {
       data = data.substr(1);

elf/passes.cc

@@ -3004,7 +3004,7 @@ void write_dependency_file(Context<E> &ctx) {
   std::unordered_set<std::string> seen;
 
   for (std::unique_ptr<MappedFile> &mf : ctx.mf_pool)
-    if (!mf->parent)
+    if (mf->is_dependency && !mf->parent)
       if (std::string path = path_clean(mf->name); seen.insert(path).second)
         deps.push_back(path);
 

test/elf/dependency-file-response-file.sh

@@ -0,0 +1,17 @@
+#!/bin/bash
+. $(dirname $0)/common.inc
+
+cat <<EOF | $CC -o $t/a.o -c -xc -
+#include <stdio.h>
+int main() {
+  printf("Hello world\n");
+}
+EOF
+
+echo "$t/a.o -Wl,-dependency-file=$t/dep" > $t/rsp
+
+$CC -B. -o $t/exe @$t/rsp
+
+grep -q '/exe:.*/a.o ' $t/dep
+grep -q '/a.o:$' $t/dep
+! grep -q '^/tmp' $t/dep || false