Demangling: define SWIFT_RUNTIME when building

This is required to ensure that we do not get ODR violations due to
LLVMSupport being linked in with multiple definitions. We would
previously miscompile the library resulting in a mixed signature
containing both `__swift::runtime::llvm::` and `::llvm::` versions of
`StringRef`.

Author: compnerd

Runtimes/Core/Demangling/CMakeLists.txt

@@ -21,7 +21,8 @@ target_compile_definitions(swiftDemangling PRIVATE
 # compiler, in order to avoid possible ODR violations if both are statically
 # linked into the same binary. (see also commit message for 5b1daa9055c99904c84862ecc313641fd9b26e63)
 target_compile_definitions(swiftDemangling PUBLIC
-    $<$<COMPILE_LANGUAGE:C,CXX>:-DSWIFT_INLINE_NAMESPACE=__runtime>)
+  -DSWIFT_RUNTIME
+  $<$<COMPILE_LANGUAGE:C,CXX>:-DSWIFT_INLINE_NAMESPACE=__runtime>)
 
 target_include_directories(swiftDemangling
   PRIVATE