[PPC64] gtest build error after JDK-8264207

In file included from jdk/src/hotspot/share/asm/assembler.hpp:450,
                 from jdk/src/hotspot/share/asm/macroAssembler.hpp:28,
                 from jdk/test/hotspot/gtest/code/test_codestrings.cpp:29:
jdk/src/hotspot/cpu/ppc/assembler_ppc.hpp:1608:15: error: inline function 'void Assembler::nop()' used but never defined [-Werror]
   inline void nop();
               ^~~

"assembler_ppc.inline.hpp" is not included in "test_codestrings.cpp".