Problem with building Clang and LLVM using Xcode

Hi,

I'm trying to build clang and llvm using Xcode. I used the following
command to generate the Xcode project:

cmake -G Xcode -DDCMAKE_INSTALL_PREFIX="path to my llvm install
directory" "path to my llvm directory"

Then I opened LLVM.xcodeproj in Xcode, and chose "clang" as the only
build scheme and hit the Build. I ran into this error:
clang: error: no such file or directory: 'path to my build
directory/lib/Debug/libPolly.a'.

/lib/Debug contains only one file - 'libPollyISL.a'. I got the same
error when I tried building from the command line:
clang: error: no such file or directory: 'my build
directory/lib/Debug/libPolly.a'
The following build commands failed: Ld
/Users/Firouzeh/dev/llvmbuild/Debug/bin/opt normal x86_64

I'm trying Xcode build, because I want to debug clang in Xcode. I'd
appreciate any help!

I'm using macOS 10.13.1, Xcode 9.1, and Apple LLVM version 9.0.0
(clang-900.0.38).

Thanks!

Firouzeh Soleymani