Build the docs with test.sh

We currently build the docs as a separate CI job, we can however just do
it as part of the `Tests` job using the nightly toolchain.

Conditionally build the docs based on a `DO_DOCS` env var.

Note, uses `--cfg docsrs` so can only be built run with nightly toolchain.

.github/workflows/rust.yml

@@ -24,6 +24,7 @@ jobs:
               DO_BENCH: true
               AS_DEPENDENCY: true
               DO_NO_STD: true
+              DO_DOCS: true
           - rust: 1.29.0
             env:
               AS_DEPENDENCY: true
@@ -82,20 +83,6 @@ jobs:
       - name: run cross test
         run: cross test --target s390x-unknown-linux-gnu
 
-  Docs:
-    name: Docs
-    runs-on: ubuntu-latest
-    steps:
-      - name: Checkout Crate
-        uses: actions/checkout@v2
-      - name: Checkout Toolchain
-        uses: actions-rs/toolchain@v1
-        with:
-          profile: minimal
-          toolchain: stable
-          override: true
-      - name: Create Doc
-        run: cargo doc
   Embedded:
     runs-on: ubuntu-latest
     steps:

contrib/test.sh

@@ -67,6 +67,11 @@ do
     cargo test --verbose --features="$feature"
 done
 
+# Build the docs if told to (this only works with the nightly toolchain)
+if [ "$DO_DOCS" = true ]; then
+    RUSTDOCFLAGS="--cfg docsrs" cargo doc --all --features="$FEATURES"
+fi
+
 # Fuzz if told to
 if [ "$DO_FUZZ" = true ]
 then