fix: WASM_API_EXTERN should get visibility("default") on gcc and clang (bytecodealliance#4851)

This allows the wasm_c_api to work in shared libraries on non-Windows
platforms.

Author: TaylorRichberger

core/iwasm/include/wasm_c_api.h

@@ -22,6 +22,8 @@
 #else
 #define WASM_API_EXTERN __declspec(dllimport)
 #endif
+#elif defined(__GNUC__) || defined(__clang__)
+#define WASM_API_EXTERN __attribute__((visibility("default")))
 #else
 #define WASM_API_EXTERN
 #endif