Only use sanitizers with default toolchain on Windows as well.

build/toolchain/gcc_toolchain.gni

Index: build/toolchain/gcc_toolchain.gni
diff --git a/build/toolchain/gcc_toolchain.gni b/build/toolchain/gcc_toolchain.gni
index 068fa0d88a7e0e3cbc1de37ec34738cc391c81c3..10a82bc42dfa4b4b6c3171aa336a040527623f4c 100644
--- a/build/toolchain/gcc_toolchain.gni
+++ b/build/toolchain/gcc_toolchain.gni
@@ -474,28 +474,6 @@ template("gcc_toolchain") {
       } else {
         v8_current_cpu = current_cpu
       }
-
-      # Disable sanitizers for non-default toolchains.
-      is_asan = false
-      is_cfi = false
-      is_lsan = false
-      is_msan = false
-      is_syzyasan = false
-      is_tsan = false
-      is_ubsan = false
-      is_ubsan_null = false
-      is_ubsan_no_recover = false
-      is_ubsan_security = false
-      is_ubsan_vptr = false
-      msan_track_origins = 0
-      sanitizer_coverage_flags = ""
-      use_cfi_diag = false
-      use_custom_libcxx = false
-      use_drfuzz = false
-      use_libfuzzer = false
-      use_prebuilt_instrumented_libraries = false
-      use_locally_built_instrumented_libraries = false
-      use_sanitizer_coverage = false
     }
 
     forward_variables_from(invoker, [ "deps" ])