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

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index a9c8f1ddefe7e811ae8472237beab9a075404911..e909a8369e88f109cc92e0b819f262976ab47898 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -5524,9 +5524,12 @@
             },
             'msvs_settings': {
               'VCLinkerTool': {
-                # Set /LTCG for the official builds.
-                'LinkTimeCodeGeneration': '1',
                 'AdditionalOptions': [
+                  # 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.
                   '/cgthreads:8',