In previous versions, the external_project module on Windows used a Windows-style path (e.g., C:/path/to/configure) to execute the configure file, and a relative path from the drive root (e.g., /path/to/prefix) as the installation prefix. However, since configure scripts are typically intended to be run in a POSIX-like environment (MSYS2, Cygwin, or GitBash), these paths were incompatible with some configure scripts.
The external_project module now uses the cygpath command to convert the configure command path and prefix to Unix-style paths (e.g., /c/path/to/configure for MSYS2 and /cygdrive/c/path/to/configure for Cygwin). If the cygpath command is not found in the PATH, it will fall back to the previous behavior.