Use minimal dependency versions for MSRV tests on CI (#1109)

internal-minimal-versions/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "internal-minimal-versions"
+version = "0.1.0"
+edition = "2021"
+publish = false
+
+# these dependencies don't build if installed with `cargo +nightly update -Z
+# minimal-versions` so we add them here to make sure we get a version that
+# does build
+#
+# this only matters for axum's CI
+[dependencies]
+crc32fast = "1.3.2"
+gcc = "0.3.55"
+time = "0.3.9"
+tungstenite = "0.17.2"

internal-minimal-versions/src/lib.rs

@@ -0,0 +1 @@
+// intentionally left empty