Revert "Reland "Consider winsdk_samples a system library.""

This reverts commit 9c9f3c9268c7d573880ef6eabd55ee12d8c46a1d.

Reason for revert: Using -imsvc warnings are still considered.

Change-Id: Ibe23541c075d8450bb839ed419af7c94cbaecbe7
Reviewed-on: https://webrtc-review.googlesource.com/76522
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>

BUILD.gn

diff --git a/BUILD.gn b/BUILD.gn
index 55f7df8..291a208 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -10,13 +10,30 @@
   baseclasses_dir = "Samples/multimedia/directshow/baseclasses"
 
   config("winsdk_samples_config") {
+    include_dirs = [ baseclasses_dir ]
+  }
+
+  config("winsdk_samples_warnings_config") {
     if (is_win && is_clang) {
       cflags = [
-        "-imsvc",
-        rebase_path(baseclasses_dir, root_build_dir)
+        # Disable warnings failing when compiling with Clang on Windows.
+        # https://bugs.chromium.org/p/webrtc/issues/detail?id=5366
+        "-Wno-comment",
+        "-Wno-delete-non-virtual-dtor",
+        "-Wno-ignored-attributes",
+        "-Wno-logical-op-parentheses",
+        "-Wno-non-pod-varargs",
+        "-Wno-microsoft-extra-qualification",
+        "-Wno-missing-braces",
+        "-Wno-overloaded-virtual",
+        "-Wno-parentheses",
+        "-Wno-reorder",
+        "-Wno-string-conversion",
+        "-Wno-tautological-constant-out-of-range-compare",
+        "-Wno-unknown-pragmas",
+        "-Wno-unused-private-field",
+        "-Wno-writable-strings",
       ]
-    } else {
-      include_dirs = [ baseclasses_dir ]
     }
   }
 
@@ -93,6 +110,7 @@
     ]
     configs += [
       "//build/config/compiler:no_chromium_code",
+      ":winsdk_samples_warnings_config",
     ]
   }
 }