Install gcc and ninja failed through the mirrors.tuna.tsinghua.edu.cn

[chucklu]

pacman -Syu mingw-w64-x86_64-gcc mingw-w64-x86_64-ninja
:: Synchronizing package databases...
clangarm64 is up to date
mingw32 is up to date
mingw64 is up to date
ucrt64 is up to date
clang32 is up to date
clang64 is up to date
msys.db failed to download
error: failed retrieving file 'msys.db' from mirrors.tuna.tsinghua.edu.cn : The requested URL returned error: 404
error: failed to synchronize all databases (unexpected error)

[chucklu]

Tried to execute command pacman -Syu mingw-w64-x86_64-gcc mingw-w64-x86_64-ninja --debug
debug: msys.db: url is https://mirrors.tuna.tsinghua.edu.cn/msys2/msys//msys.db

The pacman is trying to access the wrong url which does not contains the architecture folder
As we have three architecture folder under url https://mirrors.tuna.tsinghua.edu.cn/msys2/msys/

might related to this issue error: failed retrieving file 'msys.db' (Solved on x86_64 Windows 10)

[chucklu]

It seems the configuration in C:\msys64\etc\pacman.d\mirrorlist.msys is wrong.
The second step 修改镜像服务器 should be executed under msys2, I mistakenly executed it in cmd.exe, which caused the issue.
and file content become
Server = https://mirrors.tuna.tsinghua.edu.cn/msys2/msys//

and when I execute the command in msys2, I got new content, which is correct one
Server = https://mirrors.tuna.tsinghua.edu.cn/msys2/msys/$arch/

now the installation works

[chucklu]

@cloudwu We could explicitly change "修改镜像服务器" to "在msys2中修改镜像服务器"