Fix working directory and invocation of autoconf

[fakoor]

Remove superfluous changing directory to build (too early) Correct execution path for invoking ./configure (instead of referencing parent folder from the child with ../configure) The above fixes also help the make command execute smoothly which otherwise would have been left defunct since makefile was not present there

[gkobeaga]

I like to have the build artifacts separated from the source code. My guess is that the main problem is the LSP isn't recognizing the compilation database. In order to fix it, I have added the appropriate flag to .clang. Let me know if this helps you out.