zigup not works with https_proxy

``` $ https_proxy=http://127.0.0.1:7890 zigup fetch master ... error: could not download 'https://ziglang.org/download/index.json': the HTTP server replied with unsuccessful response '400 Bad Request' $ uname -a Darwin bogon 24.6.0 Darwin Kernel Version 24.6.0: Mon Jul 14 11:30:34 PDT 2025; root:xnu-11417.140.69~1/RELEASE_ARM64_T8103 arm64 ``` related to https://github.com/ziglang/zig/issues/19878 ?