clang-format: Fix incorrect indentation in last line of macro definition

Before:
  #define MACRO(a) \
    if (a) {       \
      f();         \
    } else         \
    g()

After:
  #define MACRO(a) \
    if (a) {       \
      f();         \
    } else         \
      g()

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@270028 91177308-0d34-0410-b5e6-96231b3b80d8