ci: bring back build tests (#1813)

This directory was deleted when `cargo hack` was introduced, however
there were some tests that were still useful (macro failure output).

Also, additional build tests will be added over time.

ci/azure-test-build.yml

@@ -0,0 +1,17 @@
+jobs:
+- job: ${{ parameters.name }}
+  displayName: ${{ parameters.displayName }}
+  pool:
+    vmImage: 'Ubuntu 16.04'
+
+  steps:
+  - template: azure-install-rust.yml
+    parameters:
+      rust_version: ${{ parameters.rust }}
+
+  - script: cargo install cargo-hack
+    displayName: Install cargo-hack
+
+  - script: cargo hack test --each-feature
+    displayName: cargo hack test --each-feature
+    workingDirectory: $(Build.SourcesDirectory)/tests-build