Use /LTCG:Incremental to speed up the non-clobber official builds.

build/config/compiler/BUILD.gn

Index: build/config/compiler/BUILD.gn
diff --git a/build/config/compiler/BUILD.gn b/build/config/compiler/BUILD.gn
index 6f462beabc05be2d25c5951ab34e2bf69624fc90..c15ab9f26bc292d73625625c7a4015e543fe83a7 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -1207,7 +1207,12 @@ if (is_win) {
   if (is_official_build) {
     common_optimize_on_ldflags += [
       "/OPT:REF",  # Remove unreferenced data.
-      "/LTCG",  # Link-time code generation.
+
+      # Enable /LTCG for the official builds. Use the incremental mode to
+      # speed-up the non-clobber builds. This is not the same as incremental
+      # linking (/INCREMENTAL) and doesn't have any impact on code size or on
+      # performance.
+      "/LTCG:INCREMENTAL",
 
       # Set the number of LTCG code-gen threads to eight. The default is four.
       # This gives a 5-10% link speedup.