[clangd] Add a build option to disable building dexp (llvm#133124)

Building dexp on Debian 11 currently causes intermittent failures [0] [1].

Adding the CLANGD_BUILD_DEXP option to disable dexp from the build
allows Debian 11 users to build clang (albeit without the dexp tool).

This option is set to "Build Dexp" by default so, no change is expected
without manual setting.

[0]: https://bugzilla.yoctoproject.org/show_bug.cgi?id=15803
[1]: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1101322

Author: ycongal-smile

clang-tools-extra/clangd/CMakeLists.txt

@@ -210,6 +210,9 @@ if (CLANGD_ENABLE_REMOTE)
   include(AddGRPC)
 endif()
 
+option(CLANGD_BUILD_DEXP "Build the dexp tool as part of Clangd" ON)
+llvm_canonicalize_cmake_booleans(CLANGD_BUILD_DEXP)
+
 if(CLANG_INCLUDE_TESTS)
   add_subdirectory(test)
   add_subdirectory(unittests)
@@ -220,4 +223,7 @@ option(CLANGD_ENABLE_REMOTE "Use gRPC library to enable remote index support for
 set(GRPC_INSTALL_PATH "" CACHE PATH "Path to gRPC library manual installation.")
 
 add_subdirectory(index/remote)
-add_subdirectory(index/dex/dexp)
+
+if(CLANGD_BUILD_DEXP)
+  add_subdirectory(index/dex/dexp)
+endif()

clang-tools-extra/clangd/test/CMakeLists.txt

@@ -3,15 +3,18 @@ set(CLANGD_TEST_DEPS
   ClangdTests
   clangd-indexer
   split-file
-  # No tests for it, but we should still make sure they build.
-  dexp
   )
 
 if(CLANGD_BUILD_XPC)
   list(APPEND CLANGD_TEST_DEPS clangd-xpc-test-client)
   list(APPEND CLANGD_TEST_DEPS ClangdXpcUnitTests)
 endif()
 
+if(CLANGD_BUILD_DEXP)
+  # No tests for it, but we should still make sure they build.
+  list(APPEND CLANGD_TEST_DEPS dexp)
+endif()
+
 if(CLANGD_ENABLE_REMOTE)
   list(APPEND CLANGD_TEST_DEPS clangd-index-server clangd-index-server-monitor)
 endif()

clang-tools-extra/clangd/test/lit.site.cfg.py.in

@@ -15,6 +15,7 @@ config.llvm_shlib_dir = "@SHLIBDIR@"
 config.clangd_source_dir = "@CMAKE_CURRENT_SOURCE_DIR@/.."
 config.clangd_binary_dir = "@CMAKE_CURRENT_BINARY_DIR@/.."
 config.clangd_build_xpc = @CLANGD_BUILD_XPC@
+config.clangd_build_dexp = @CLANGD_BUILD_DEXP@
 config.clangd_enable_remote = @CLANGD_ENABLE_REMOTE@
 config.clangd_tidy_checks = @CLANGD_TIDY_CHECKS@
 config.have_zlib = @LLVM_ENABLE_ZLIB@