chore: keep rust version up-to-date with stable channel in CI

.github/workflows/build.yml

@@ -3,7 +3,7 @@ on: [push, pull_request]
 
 jobs:
   test:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v2
     - name: Cache cargo bin
@@ -16,7 +16,7 @@ jobs:
     - name: Test
       run: make test
   nits:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v2
     - name: Install cargo deadlinks
@@ -25,4 +25,4 @@ jobs:
         chmod +x ~/.cargo/bin/cargo-deadlinks
         cargo deadlinks --version
     - name: Nits
-      run: make nits
+      run: make nits

Makefile

@@ -2,6 +2,7 @@ all: test nits
 
 .PHONY: test
 test:
+	rustup update
 	cargo test --release
 	cargo test --release --features=lp
 	# don't run examples in proof-production mode
@@ -10,6 +11,7 @@ test:
 
 .PHONY: nits
 nits:
+	rustup update
 	rustup component add rustfmt clippy
 	cargo fmt -- --check
 	cargo clean --doc
@@ -23,4 +25,4 @@ nits:
 
 .PHONY: docs
 docs:
-	RUSTDOCFLAGS="--cfg docsrs" cargo +nightly doc --all-features --open
+	RUSTDOCFLAGS="--cfg docsrs" cargo +nightly doc --all-features --open