Don't attempt to build a local copy of GoogleTest.

--- third_party/CMakeLists.txt.orig	2023-09-14 17:41:15 UTC
+++ third_party/CMakeLists.txt
@@ -1,13 +1,3 @@ endif()
 if(BUILD_LLVM_DWARF)
   add_subdirectory(llvm-project)
 endif()
-
-include_directories(
-  googletest/googletest
-  googletest/googletest/include
-)
-
-if(BUILD_TESTS)
-  add_library(gtest STATIC googletest/googletest/src/gtest-all.cc)
-  add_library(gtest_main STATIC googletest/googletest/src/gtest_main.cc)
-endif()