ci: download curl and openssl from s3 for dist-x86_64-linux

CentOS 5 only supports SSLv3 without SNI, and to get newer protocols
working we need to download and compile OpenSSL and cURL from our
mirror. Because of that, we can't use the CDN, as CloudFront requires
TLSv1 with SNI.

This commit changes the dist-x86_64-linux image to bypass the CDN for
OpenSSL and cURL.

Author: pietroalbini

src/ci/docker/dist-x86_64-linux/build-curl.sh

@@ -5,7 +5,10 @@ source shared.sh
 
 VERSION=7.66.0
 
-curl https://ci-mirrors.rust-lang.org/rustc/curl-$VERSION.tar.xz \
+# This needs to be downloaded directly from S3, it can't go through the CDN.
+# That's because the CDN is backed by CloudFront, which requires SNI and TLSv1
+# (without paying an absurd amount of money).
+curl https://rust-lang-ci-mirrors.s3-us-west-1.amazonaws.com/rustc/curl-$VERSION.tar.xz \
   | xz --decompress \
   | tar xf -
 

src/ci/docker/dist-x86_64-linux/build-openssl.sh

@@ -4,7 +4,11 @@ set -ex
 source shared.sh
 
 VERSION=1.0.2k
-URL=https://ci-mirrors.rust-lang.org/rustc/openssl-$VERSION.tar.gz
+
+# This needs to be downloaded directly from S3, it can't go through the CDN.
+# That's because the CDN is backed by CloudFront, which requires SNI and TLSv1
+# (without paying an absurd amount of money).
+URL=https://rust-lang-ci-mirrors.s3-us-west-1.amazonaws.com/rustc/openssl-$VERSION.tar.gz
 
 curl $URL | tar xzf -