[libcxx] [test] Fix the nasty_macros test on Windows on ARM/ARM64

[mstorsjo]

Summary

This isn't a configuration that we unfortunately can add to
the CI practically at the moment, but I do run the tests
sporadically offline in this configuration.

libcxx/test/libcxx/nasty_macros.compile.pass.cpp

 #define Arg NASTY_MACRO
 #define Args NASTY_MACRO
 #define As NASTY_MACRO
 #define B NASTY_MACRO
 #define Bs NASTY_MACRO
 #define C NASTY_MACRO
 #define Cp NASTY_MACRO
 #define Cs NASTY_MACRO
-#define D NASTY_MACRO
+// Windows setjmp.h contains a struct member named 'D' on ARM/AArch64.
+#ifndef _WIN32
+# define D NASTY_MACRO
+#endif
 #define Dp NASTY_MACRO
 #define Ds NASTY_MACRO
 #define E NASTY_MACRO
 #define Ep NASTY_MACRO
 #define Es NASTY_MACRO
 #define R NASTY_MACRO
 #define Rp NASTY_MACRO
 #define Rs NASTY_MACRO