[bazel] add missing header to bolt build file

Author: durin42

utils/bazel/llvm-project-overlay/bolt/BUILD.bazel

@@ -255,6 +255,7 @@ cc_library(
     srcs = glob([
         "lib/Target/AArch64/*.cpp",
     ]),
+    hdrs = ["lib/Target/AArch64/AArch64MCSymbolizer.h"],
     includes = ["include"],
     deps = [
         ":Core",