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()

llvm-svn: 270028