Only use /Gw in non-ASan builds on Windows

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index d1492320f727797ac8f4fb5c39ea091aba0eacf6..bf3e7785d935cf81520a2102d362b43463fc221f 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -3372,11 +3372,18 @@
                 # "/Oy /Oy-" and warnings about overriding.
                 'AdditionalOptions': ['/Oy-'],
               }],
+              ['asan==0', {
+                # Put data in separate COMDATs. This allows the linker
+                # to put bit-identical constants at the same address even if
+                # they're unrelated constants, which saves binary size.
+                # This optimization can't be used when ASan is enabled because
+                # it is not compatible with the ASan ODR checker.
+                'AdditionalOptions': ['/Gw'],
+              }],
             ],
             'AdditionalOptions': [
                 '/d2Zi+',  # Improve debugging of Release builds.
                 '/Zc:inline',  # Remove unreferenced COMDAT (faster links).
-                '/Gw',  # Put data in separate COMDATs.
                 '<@(win_release_extra_cflags)',
             ],
           },