http: fix build error on FreeBSD

The `result` parameter passed to `http_request_reauth()` may either
point to a `struct strbuf` or a `FILE *`, where the `target` parameter
tells us which of either it actually is. To accommodate for both types
the pointer is a `void *`, which we then pass directly to functions
without doing a cast.

This is fine on most platforms, but it breaks on FreeBSD because
`fileno()` is implemented as a macro that tries to directly access the
`FILE *` structure.

Fix this issue by storing the `FILE *` in a local variable before we
pass it on to other functions.

Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Taylor Blau <[email protected]>

Author: pks-t

http.c

@@ -2290,17 +2290,19 @@ static int http_request_reauth(const char *url,
 		case HTTP_REQUEST_STRBUF:
 			strbuf_reset(result);
 			break;
-		case HTTP_REQUEST_FILE:
-			if (fflush(result)) {
+		case HTTP_REQUEST_FILE: {
+			FILE *f = result;
+			if (fflush(f)) {
 				error_errno("unable to flush a file");
 				return HTTP_START_FAILED;
 			}
-			rewind(result);
-			if (ftruncate(fileno(result), 0) < 0) {
+			rewind(f);
+			if (ftruncate(fileno(f), 0) < 0) {
 				error_errno("unable to truncate a file");
 				return HTTP_START_FAILED;
 			}
 			break;
+		}
 		default:
 			BUG("Unknown http_request target");
 		}