gn: define and use clang_base_path

build/sanitizers/BUILD.gn

Index: build/sanitizers/BUILD.gn
diff --git a/build/sanitizers/BUILD.gn b/build/sanitizers/BUILD.gn
index 40ffcb7469d052abf6581f3732c6a1a7a21e5351..473200f299abfe6181210649d4d8e33e8b5f264f 100644
--- a/build/sanitizers/BUILD.gn
+++ b/build/sanitizers/BUILD.gn
@@ -2,18 +2,20 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//build/config/clang/clang.gni")
+
 if (is_clang) {
   copy("copy_llvm_symbolizer") {
     if (is_win) {
       sources = [
-        "//third_party/llvm-build/Release+Asserts/bin/llvm-symbolizer.exe",
+        "$clang_base_path/bin/llvm-symbolizer.exe",
       ]
       outputs = [
         "$root_out_dir/llvm-symbolizer.exe",
       ]
     } else {
       sources = [
-        "//third_party/llvm-build/Release+Asserts/bin/llvm-symbolizer",
+        "$clang_base_path/bin/llvm-symbolizer",
       ]
       outputs = [
         "$root_out_dir/llvm-symbolizer",