Reintroduce alwaysinline and nodebug as fallbacks to SWIFT_INLINE_THUNK_ATTRIBUTES

If the C++ compiler doesn't support the transparent_stepping attribute,
fallback to annotating inline thunks with the alwaysinline and nodebug
attributes.

(cherry picked from commit cfb3e5a)

Author: augusto2112

lib/PrintAsClang/_SwiftCxxInteroperability.h

@@ -30,18 +30,21 @@
 
 #if __has_attribute(always_inline) && __has_attribute(nodebug)
 #define SWIFT_INLINE_THUNK_ATTRIBUTES                                          \
-  __attribute__((always_inline)) __attribute__((nodebug))
+  __attribute__((transparent_stepping))
+#elif __has_attribute(always_inline) && __has_attribute(nodebug)
+ #define SWIFT_INLINE_THUNK_ATTRIBUTES                                          \
+   __attribute__((always_inline)) __attribute__((nodebug))
+#else
+#define SWIFT_INLINE_THUNK_ATTRIBUTES
+#endif
+
 #if defined(DEBUG) && __has_attribute(used)
 // Additional 'used' attribute is used in debug mode to make inline thunks
 // accessible to LLDB.
 #define SWIFT_INLINE_THUNK_USED_ATTRIBUTE __attribute__((used))
 #else
 #define SWIFT_INLINE_THUNK_USED_ATTRIBUTE
 #endif
-#else
-#define SWIFT_INLINE_THUNK_ATTRIBUTES
-#define SWIFT_INLINE_THUNK_USED_ATTRIBUTE
-#endif
 
 /// The `SWIFT_INLINE_THUNK` macro is applied on the inline function thunks in
 /// the header that represents a C/C++ Swift module interface generated by the