[clangd] Really fix clang -Wimplicit-fallthrough
[clangd] Really fix clang -Wimplicit-fallthrough

The intention was to fall through to Function case in LLVM_ENABLE_ASSERTIONS=Off builds.

Use #ifndef NDEBUG to fix -Wimplicit-fallthrough

git-svn-id: a34e9779ed74578ad5922b3306b3d80a0c825546@345953 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/clang-tools-extra,llvm-mirror/clang-tools-extra,llvm-mirror/clang-tools-extra,llvm-mirror/clang-tools-extra