==> Installing dependencies for crystal: llvm
==> Installing crystal dependency: llvm
Warning: Building llvm from source:
  The bottle needs the Xcode CLT to be installed.
==> Downloading https://releases.llvm.org/6.0.1/llvm-6.0.1.src.tar.xz
Already downloaded: /Users/dan/Library/Caches/Homebrew/downloads/7cac209bbcafb1e41b0b73a8b4b87f20ac9c6382142420636f0a0beab0a8b35d--llvm-6.0.1.src.tar.xz
==> Downloading https://releases.llvm.org/6.0.1/cfe-6.0.1.src.tar.xz
Already downloaded: /Users/dan/Library/Caches/Homebrew/downloads/a0b4de455939c63eb3c9ee778d4303c4289c41a66d0619e54ae008c6602f69bf--cfe-6.0.1.src.tar.xz
==> Downloading https://releases.llvm.org/6.0.1/clang-tools-extra-6.0.1.src.tar.xz
Already downloaded: /Users/dan/Library/Caches/Homebrew/downloads/7e8c00a4fa00b087b576401933607e227fc41749feef1c5f638c751882c11423--clang-tools-extra-6.0.1.src.tar.xz
==> Downloading https://releases.llvm.org/6.0.1/openmp-6.0.1.src.tar.xz
Already downloaded: /Users/dan/Library/Caches/Homebrew/downloads/9acbc218fbe4cf65d4e86ed611df6efcdab0d4ccc1fad302e581eaf91a9265c0--openmp-6.0.1.src.tar.xz
==> Downloading https://releases.llvm.org/6.0.1/libcxx-6.0.1.src.tar.xz
Already downloaded: /Users/dan/Library/Caches/Homebrew/downloads/9213edc06aa46e6a3a2ea99cd93c67f6f73f7a731973e1f18a3afbe9a0175375--libcxx-6.0.1.src.tar.xz
==> Downloading https://releases.llvm.org/6.0.1/libunwind-6.0.1.src.tar.xz
Already downloaded: /Users/dan/Library/Caches/Homebrew/downloads/772c1b97e40817225a8f78ee4b2d07a6e5cf26c4c1d8ebcc1b3ae2edd9142430--libunwind-6.0.1.src.tar.xz
==> Downloading https://releases.llvm.org/6.0.1/lld-6.0.1.src.tar.xz
Already downloaded: /Users/dan/Library/Caches/Homebrew/downloads/80cf9a655c73f99526607c712cace18cd7e7aea33d1aadb9dbc5ecad0b583600--lld-6.0.1.src.tar.xz
==> Downloading https://releases.llvm.org/6.0.1/polly-6.0.1.src.tar.xz
Already downloaded: /Users/dan/Library/Caches/Homebrew/downloads/d59ff2485c480be5e9df6540941a4878704f60bd26963d304d5c8eb82c8a8b2d--polly-6.0.1.src.tar.xz
==> Downloading https://releases.llvm.org/6.0.1/compiler-rt-6.0.1.src.tar.xz
Already downloaded: /Users/dan/Library/Caches/Homebrew/downloads/074fa28ae10d06c5c9701595ac5da7a6abd1a914dca84e48adce7ca22185c303--compiler-rt-6.0.1.src.tar.xz
==> cmake -G Unix Makefiles /private/tmp/llvm-20180911-43547-1vkjhlt/llvm-6.0.1.src -DCMAKE_C_FLAGS_RELEASE=-DNDEBUG -DCMAKE_CX
==> make