Fix environment variable configuration in FAQ
In bash, the variable is set using "export".
@@ -103,7 +103,7 @@ You could overwrite the `adb` binary in the other program, or ask _scrcpy_ to
use a specific `adb` binary, by setting the `ADB` environment variable:
```bash
-set ADB=/path/to/your/adb
+export ADB=/path/to/your/adb
scrcpy
```
