Opt-in to the Windows SegmentHeap

This heap offers vastly more efficient multi-threaded operations. Local
testing shows a reduction in generation for Chrome on the order of 50% -
83% (from >72s down to <12s in one config; 17s down to 8s in another).

Change-Id: Icf8be8de86652d0b343050d5f08427aae2c29dad
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/20520
Reviewed-by: Andrew Grieve <agrieve@google.com>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>

build/windows.manifest.xml

diff --git a/build/windows.manifest.xml b/build/windows.manifest.xml
index 6058750..e6a9857 100644
--- a/build/windows.manifest.xml
+++ b/build/windows.manifest.xml
@@ -4,10 +4,13 @@
 See: https://docs.microsoft.com/en-us/windows/win32/sbscs/application-manifests
 -->
 <assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0" xmlns:asmv3="urn:schemas-microsoft-com:asm.v3">
-    <!-- Remove (most) legacy path limits -->
-    <asmv3:application>
-        <asmv3:windowsSettings xmlns:ws2="http://schemas.microsoft.com/SMI/2016/WindowsSettings">
-            <ws2:longPathAware>true</ws2:longPathAware>
-        </asmv3:windowsSettings>
-    </asmv3:application>
-</assembly>
\ No newline at end of file
+  <!-- Remove (most) legacy path limits -->
+  <asmv3:application>
+    <asmv3:windowsSettings
+        xmlns:ws2="http://schemas.microsoft.com/SMI/2016/WindowsSettings"
+        xmlns:ws3="http://schemas.microsoft.com/SMI/2020/WindowsSettings">
+      <ws2:longPathAware>true</ws2:longPathAware>
+      <ws3:heapType>SegmentHeap</ws3:heapType>
+    </asmv3:windowsSettings>
+  </asmv3:application>
+</assembly>