[llvm-objcopy] Add support for response files in llvm-strip and llvm-objcopy

Summary: Addresses https://bugs.llvm.org/show_bug.cgi?id=42671

Reviewers: jhenderson, espindola, alexshap, rupprecht

Reviewed By: jhenderson

Subscribers: seiya, emaste, arichardson, jakehehrlich, MaskRay, abrachet, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D65372

llvm-svn: 371911
diff --git a/llvm/docs/CommandGuide/llvm-strip.rst b/llvm/docs/CommandGuide/llvm-strip.rst
index a4f497a..546a0a2 100644
--- a/llvm/docs/CommandGuide/llvm-strip.rst
+++ b/llvm/docs/CommandGuide/llvm-strip.rst
@@ -104,6 +104,10 @@
 
  Display the version of this program.
 
+.. option:: @<FILE>
+
+  Read command-line options and commands from response file `<FILE>`.
+
 COFF-SPECIFIC OPTIONS
 ---------------------