Because the standard for configure scripts says that the current directory at invocation is the build directory and the location of the configure script is the source directory. You are expected to be able to have multiple build directories if you want them. If you have written your configure script correctly, than in-tree builds (srcdir == builddir) also work, but most people don't want that anyway.
You can. But this makes intent clear. If you clone a git repo and see build/ with only a gitkeep, you are safe to bet your life savings on that being the compiled assets dir.
Comments
qemu: mkdir build; cd build; ../configure, some projects are like that
Why can’t the configure script do this?
Because the standard for configure scripts says that the current directory at invocation is the build directory and the location of the configure script is the source directory. You are expected to be able to have multiple build directories if you want them. If you have written your configure script correctly, than in-tree builds (srcdir == builddir) also work, but most people don't want that anyway.
You can. But this makes intent clear. If you clone a git repo and see build/ with only a gitkeep, you are safe to bet your life savings on that being the compiled assets dir.