Allow external definition of MRB_API macro
When building WebAssembly targets with clang (e.g. wasm32-unknown-unknown), all
symbols are hidden by default. To export a symbol, it must be marked with
__attribute__((visibility(default)))
Rather than detecting this exotic target in mruby, allow MRB_API to be defined
externally.
@@ -62,6 +62,7 @@ MRB_BEGIN_DECL
#define MRB_INLINE static inline
/** Declare a public MRuby API function. */
+#ifndef MRB_API
#if defined(MRB_BUILD_AS_DLL)
#if defined(MRB_CORE) || defined(MRB_LIB)
# define MRB_API __declspec(dllexport)
@@ -71,6 +72,7 @@ MRB_BEGIN_DECL
#else
# define MRB_API extern
#endif
+#endif
MRB_END_DECL
