Final fixes for make test-capi on windows-msvc

- .wasm files should always be opened in "rb" mode
- open_memstream doesn't exist on Windows, use tempfile() instead
- remove .obj and .exe files when the test finish

lib/c-api/examples/early-exit.c

@@ -45,7 +45,7 @@ int main(int argc, const char *argv[]) {
 
   // Load binary.
   printf("Loading binary...\n");
-  FILE *file = fopen("assets/call_trap.wasm", "r");
+  FILE *file = fopen("assets/call_trap.wasm", "rb");
   if (!file) {
     printf("> Error loading module!\n");
     return 1;