Fix no-inline compiler flag on Windows

-fno-inline is unavailable on clang-cl nor cl.exe, and causes a build
failure on Windows bot.
This CL updates that flag to "/Ob0", which is msvc-equivalent of
-fno-inline.

Change-Id: Id9ffed03a855ac0b773ee28625472de664c3cb30
Reviewed-on: https://chromium-review.googlesource.com/c/1442013Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Taiju Tsuiki <tzik@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59185}

BUILD.gn

@@ -593,10 +593,14 @@ config("toolchain") {
   }
 
   if (v8_no_inline) {
-    cflags += [
-      "-fno-inline-functions",
-      "-fno-inline",
-    ]
+    if (is_win) {
+      cflags += [ "/Ob0" ]
+    } else {
+      cflags += [
+        "-fno-inline-functions",
+        "-fno-inline",
+      ]
+    }
   }
 
   if (is_clang) {