install-from-bindep needs PIP_OPTS

The install-from-bindep script should also incorporate `PIP_OPTS="${PIP_OPTS-}"` as is already done in the assemble script to allow for custom pip options.

Current workaround is to set your own `ARG CONSTRAINTS=` in a Containerfile to use that var, which could get overwritten by the builder

从 install-from-bindep 脚本开始，并比较 assemble 脚本如何处理 PIP_OPTS。确认现有的 bindep 安装路径和当前的 Containerfile workaround，然后验证自定义 pip 选项在不依赖被覆盖的 ARG 的情况下仍能保留。

由索引模型根据 Issue 内容生成。