Make sure that cmake generate build files in current dir

[meowtec]

This should fix the Error: could not load cache BUG.

If there are already generated build files in the project directory, then if you execute the command cmake path/project in $OUT_DIR/build, cmake will not generate new build files in the $OUT_DIR/build directory.

So -B . is needed. https://cmake.org/cmake/help/latest/manual/cmake.1.html#cmdoption-cmake-B

Example:

cd /path/to/project
cmake .         
# output `Build files have been written to: /path/to/project`
cd /path/to/build && cmake /path/to/project
# we expect the build files will be generated at current dir (/path/to/build)
# but unfortunately get `Build files have been written to: /path/to/project`
cd /path/to/build && cmake /path/to/project -B .  
# output `Build files have been written to: /path/to/build`, that is right!

Infomation:

cmake --version
cmake version 3.27.7

CMake suite maintained and supported by Kitware (kitware.com/cmake).

[tgross35]

To be clear, the problem is that when you configure a probject with cmake-rs and then try to build/reconfigure via the cmake binary directly, it doesn't work?

This fix makes sense, but I think we should use an absolute path to avoid any possible problems related to the location of .. So two requested changes:

1. Set -B right after here, so we set both the CWD and the -B flag

   cmake-rs/src/lib.rs

   Line 585 in fd56c5a

   cmd.arg(&self.path).current_dir(&build);

2. A few lines up, change let build = dst.join("build"); to:

   let build_dir = dst.join("build");
   let build_dir = build_dir.canonicalize().unwrap_or_else(|| build_dir.clone);

   This is preexisting but makes sure we are avoiding relative links. (also make the var name more clear)

(sorry for the delay here, this crate doesn't have a lot of maintenance)

[tgross35]

I wound up doing the second bit in #250, so all that's needed is for this to be updated to use build_dir rather than ..