When building kahlee packages, libva-amdgpu-driver is broken.

Canary builder have been failing since Jan 12.

https://uberchromegw.corp.google.com/i/chromeos/builders/kahlee-release

Interestingly, kahlee-paladin is green. This basically means that CQ for some reason didn't rebuild the libva-amdgpu-driver package or its dependencies and therefore lets bad bad CL in. 
I can however, reproduce the error by forcing a clean build of packages using CL 867671 (CL 867671 forces paladin builders to build all packages from source instead of pulling in prebuilt binaries).

$ cros tryjob -g 867671 kahlee-paladin-tryjob.
The corresponding tryjob failed.

https://uberchromegw.corp.google.com/i/chromiumos.tryserver/builders/paladin/builds/4973

Logs:

libva-amdgpu-driver-17.2.3-r2: ./configure: line 22995: /build/kahlee/usr/bin/llvm-config-host: No such file or directory
libva-amdgpu-driver-17.2.3-r2: ./configure: line 22978: /build/kahlee/usr/bin/llvm-config-host: No such file or directory
libva-amdgpu-driver-17.2.3-r2: ./configure: line 22997: /build/kahlee/usr/bin/llvm-config-host: No such file or directory
libva-amdgpu-driver-17.2.3-r2: ./configure: line 22998: /build/kahlee/usr/bin/llvm-config-host: No such file or directory
libva-amdgpu-driver-17.2.3-r2: checking for LIBDRM... yes
libva-amdgpu-driver-17.2.3-r2: checking for WAYLAND_SCANNER... no
libva-amdgpu-driver-17.2.3-r2: checking for wayland-scanner... :
libva-amdgpu-driver-17.2.3-r2: configure: WARNING: EGL platform drm needs gbm
libva-amdgpu-driver-17.2.3-r2: checking for EXPAT... yes
libva-amdgpu-driver-17.2.3-r2: checking for VL... yes
libva-amdgpu-driver-17.2.3-r2: checking for VA... yes
libva-amdgpu-driver-17.2.3-r2: checking for RADEON... yes
libva-amdgpu-driver-17.2.3-r2: checking for AMDGPU... yes
libva-amdgpu-driver-17.2.3-r2: ./configure: line 23046: test: : integer expression expected
libva-amdgpu-driver-17.2.3-r2: ./configure: line 23052: test: : integer expression expected
libva-amdgpu-driver-17.2.3-r2: configure: error: LLVM 3.9.0 or newer is required for radeonsi