Fix the build by adding trailing whitespace as mandated by GCC

base/no_copy_semantics.h:38:32: error: backslash-newline at end of file [-Werror]
 #define NO_COPY_SEMANTICS(cls) \
 ^
base/no_construction.h:54:30: error: backslash-newline at end of file [-Werror]
 #define NO_CONSTRUCTION(cls) \
 ^