Revert "Don't build clangd for mingw"

Bug: http://b/115807768

This reverts commit bbd503d792e9a9b3a726d6522962964f9cffb22b.  This can
now build succesfully with Clang.

Test: build.py
diff --git a/CMakeLists.txt b/CMakeLists.txt
index ba018e9..c3137ad 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -8,11 +8,7 @@
 add_subdirectory(clang-doc)
 add_subdirectory(clang-query)
 add_subdirectory(clang-move)
-
-if ( NOT MINGW )
 add_subdirectory(clangd)
-endif()
-
 add_subdirectory(include-fixer)
 add_subdirectory(pp-trace)
 add_subdirectory(tool-template)