win/arm64: Enable dependency tracking for #includes in asm files

(…in clang builds, which all win/arm64 builds I know are, and which
is the only supported Chromium compiler on Windows.)

Bug: 41492173
Change-Id: I5e88fdabcb57ed34c9523fdd60bea851ff62fdd6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6044022
Reviewed-by: Hans Wennborg <hans@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1387018}

build/toolchain/win/toolchain.gni

@@ -263,8 +263,9 @@ template("msvc_toolchain") {
             # Flip the slashes so that copy/paste of the command works.
             ml = string_replace(ml, "/", "\\")
           }
-          ml += " -c -o{{output}}"
+          ml += " -c -o{{output}} $show_includes"
           is_msvc_assembler = false
+          depsformat = "msvc"
         } else {
           # Only affects Arm builds with is_clang = false, implemented for
           # building V8 for Windows on Arm systems with the MSVC toolchain.