Stop passing --rsp-quoting to clang-cl.

We no longer use rsp files for compiles as of
https://chromium-review.googlesource.com/832593

Bug: 796021
Change-Id: I2ffb54f5bf2a596025af9a43d9e06fd992234f48
Reviewed-on: https://chromium-review.googlesource.com/997994Reviewed-by: Hans Wennborg <hans@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#548475}

build/toolchain/win/BUILD.gn

@@ -94,15 +94,7 @@ template("msvc_toolchain") {
       toolchain_uses_clang = is_clang
     }
 
-    if (toolchain_uses_clang && host_os != "win") {
-      # This toolchain definition uses response files for compilations.  GN uses
-      # the quoting rules of the host OS, while clang-cl always defaults to
-      # cmd.exe quoting rules for parsing response files.  Tell clang-cl to use
-      # POSIX quoting rules, so it can understand what GN generates.
-      cl = "${invoker.cl} --rsp-quoting=posix"
-    } else {
-      cl = invoker.cl
-    }
+    cl = invoker.cl
 
     if (toolchain_uses_clang && use_clang_static_analyzer) {
       analyzer_prefix =