<stdatomic.h>: Simplify preprocessor logic (#2615)

stl/inc/stdatomic.h

@@ -7,17 +7,15 @@
 #ifndef _STDATOMIC_H_
 #define _STDATOMIC_H_
 
-#if defined(RC_INVOKED) || defined(Q_MOC_RUN) || defined(__midl)
-// do nothing, see _STL_COMPILER_PREPROCESSOR in yvals_core.h
-#else // ^^^ non-compiler tools / C and C++ compilers vvv
+// see _STL_COMPILER_PREPROCESSOR in yvals_core.h
+#if !defined(RC_INVOKED) && !defined(Q_MOC_RUN) && !defined(__midl)
+
 // provide a specific error message for C compilers, before the general error message in yvals_core.h
 #ifndef __cplusplus
 #error <stdatomic.h> is not yet supported when compiling as C, but this is planned for a future release.
 #endif // __cplusplus
-#endif // ^^^ C and C++ compilers ^^^
 
 #include <yvals.h>
-#if _STL_COMPILER_PREPROCESSOR
 
 #ifdef _M_CEE_PURE
 #error <stdatomic.h> is not supported when compiling with /clr:pure.
@@ -135,5 +133,5 @@ _STL_RESTORE_CLANG_WARNINGS
 #pragma pack(pop)
 #endif // ^^^ _HAS_CXX23 ^^^
 
-#endif // _STL_COMPILER_PREPROCESSOR
+#endif // !defined(RC_INVOKED) && !defined(Q_MOC_RUN) && !defined(__midl)
 #endif // _STDATOMIC_H_