Index: lldb/tools/debugserver/source/CMakeLists.txt
===================================================================
--- lldb/tools/debugserver/source/CMakeLists.txt
+++ lldb/tools/debugserver/source/CMakeLists.txt
@@ -62,6 +62,14 @@
 
 set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -stdlib=libc++ -Wl,-sectcreate,__TEXT,__info_plist,${CMAKE_CURRENT_SOURCE_DIR}/../resources/lldb-debugserver-Info.plist")
 
+# Remove any module flags as the debugserver contains ObjC++ code which probably won't work
+# with Clang modules.
+string(REGEX REPLACE "-fmodules-cache-path=[^ ]+" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+string(REGEX REPLACE "-fmodules-local-submodule-visibility" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+string(REGEX REPLACE "-fmodules" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+string(REGEX REPLACE "-gmodules" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+string(REGEX REPLACE "-fcxx-modules" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+
 check_cxx_compiler_flag("-Wno-gnu-zero-variadic-macro-arguments"
                         CXX_SUPPORTS_NO_GNU_ZERO_VARIADIC_MACRO_ARGUMENTS)
 if (CXX_SUPPORTS_NO_GNU_ZERO_VARIADIC_MACRO_ARGUMENTS)