[gn] fix up d896e28

That commit already added the new .cpp file to the gn build, but it
missed adding the new dependency to DebugInfoGSYM to Symbolize.

Author: nico

llvm/utils/gn/secondary/llvm/lib/DebugInfo/Symbolize/BUILD.gn

@@ -4,6 +4,7 @@ static_library("Symbolize") {
     "//llvm/include/llvm/Config:config",
     "//llvm/lib/DebugInfo/BTF",
     "//llvm/lib/DebugInfo/DWARF",
+    "//llvm/lib/DebugInfo/GSYM",
     "//llvm/lib/DebugInfo/PDB",
     "//llvm/lib/Demangle",
     "//llvm/lib/Object",