Use LLVM 9 in CI

 * Trying to pin the LLVM Version to LLVM 9
 * Install LLVM@9 from Brew
 * Pin the brew version too.
 * Update macOS Build Image
 * Dump Toolchain Version on Build

   Get version information for `clang` and `rustc`. Clang is used for
   linking so knwing the LLVM Version it is using is useful.
 * Update Ubuntu Base Box
 * Ubuntu 20
 * Add LLVM 9 to Path on Linux

.ci/Dockerfile

@@ -1,11 +1,11 @@
-FROM ubuntu:18.04
-RUN apt-get update && \
-	apt-get install -y curl gnupg2 && \
-	curl -sS https://apt.llvm.org/llvm-snapshot.gpg.key | apt-key add -
-COPY llvm.list /etc/apt/sources.list.d/
+FROM ubuntu:20.04
 RUN apt-get update && \
+	apt-get install -y wget curl gnupg2 lsb-release software-properties-common && \
+	curl -O https://apt.llvm.org/llvm.sh && \
+	chmod +x llvm.sh && \
+	./llvm.sh 9 && \
 	apt-get install -y sudo && \
 	apt-get install -y python3 && \
-	apt-get install -y clang binutils && \
 	apt-get install -y llvm-9-dev && \
+	apt-get install -y clang binutils && \
 	apt-get install -y zlib1g-dev

.ci/buildbase-pipelines.yaml

@@ -3,7 +3,7 @@ pool:
 
 trigger:
   paths:
-    include: 
+    include:
       - '.ci'
 
 variables:
@@ -17,4 +17,4 @@ steps:
     docker push $(dockerId)/$(imageName)
   workingDirectory: .ci
   env:
-    pswd: $(dockerPassword)            
+    pswd: $(dockerPassword)

azure-pipelines.yaml

@@ -7,16 +7,17 @@ resources:
 jobs:
 - job: macOS
   pool:
-    vmImage: 'macOS-10.14'
+    vmImage: 'macOS-10.15'
   steps:
-    - script: 'brew install llvm'
+    - script: 'brew install llvm\@9'
       displayName: Brew install LLVM
     - script: "curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs -o rustup.sh && sh rustup.sh -y"
       displayName: Rustup
     - script: |
         export PATH=/usr/local/bin:$PATH             # Local bin (brew)
         source ~/.cargo/env
-        export LLVM_SYS_90_PREFIX=/usr/local/opt/llvm
+        export LLVM_SYS_90_PREFIX=/usr/local/opt/llvm\@9
+        export LLVM_CONFIG_PATH=${LLVM_SYS_90_PREFIX}/bin/llvm-config
         cargo install just
         ./build.sh test
       displayName: './build.sh test'
@@ -33,8 +34,9 @@ jobs:
       displayName: Rustup
     - script: |
         source ~/.cargo/env
-        export PATH=${PATH}:~/.local/bin/
+        export PATH=${PATH}:~/.local/bin/:/usr/lib/llvm-9/bin
         export LLVM_SYS_90_PREFIX=/usr/lib/llvm-9
+        export LLVM_CONFIG_PATH=${LLVM_SYS_90_PREFIX}/bin/llvm-config
         cargo install just
         ./build.sh test
       displayName: './build.sh test'

build.sh

@@ -11,4 +11,10 @@ function check_for()
 
 check_for python3
 
+echo "Clang version:"
+clang --version
+
+echo "Rust version"
+rustc --version
+
 just "$@"