clang-format: Fix bad merging of lines in nested blocks.

Before:
  SomeFunction([]() {
  #define A a
    return 43; });

After:
  SomeFunction([]() {
  #define A a
    return 43;
  });

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@220684 91177308-0d34-0410-b5e6-96231b3b80d8