Update rustup (rust-lang#2095)

Co-authored-by: Zyad Hassan <[email protected]>
Co-authored-by: Adrian Palacios <[email protected]>

Author: 3 people

docs/src/build-from-source.md

@@ -30,7 +30,7 @@ git submodule update --init
 ./scripts/setup/ubuntu/install_deps.sh
 ./scripts/setup/ubuntu/install_cbmc.sh
 ./scripts/setup/ubuntu/install_viewer.sh
-# If you haven't already:
+# If you haven't already (or from https://rustup.rs/):
 ./scripts/setup/install_rustup.sh
 source $HOME/.cargo/env
 ```
@@ -47,7 +47,7 @@ git submodule update --init
 ./scripts/setup/macos/install_deps.sh
 ./scripts/setup/macos/install_cbmc.sh
 ./scripts/setup/macos/install_viewer.sh
-# If you haven't already:
+# If you haven't already (or from https://rustup.rs/):
 ./scripts/setup/install_rustup.sh
 source $HOME/.cargo/env
 ```

scripts/setup/install_rustup.sh

@@ -5,5 +5,5 @@
 set -eux
 
 # Install Rust toolchain
-curl https://sh.rustup.rs -sSf | sh -s -- -y \
+curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y \
   && source  ~/.cargo/env