ci: update known rust version

Update RUST_VERSION_KNOWN to the latest stable known to succeed. Also
updates the documentation to avoid confusion around the use of this
variable.

diff --git a/.github/workflows/builds.yml b/.github/workflows/builds.yml
index c18358a0e0cc89a73e028fc0d1936137be37c936..f2716088be5ef7a56858c87979b6e23aa8954d21 100644 (file)
--- a/.github/workflows/builds.yml
+++ b/.github/workflows/builds.yml
@@ -22,8 +22,10 @@ env:
   # Apt sometimes likes to ask for user input, this will prevent that.
   DEBIAN_FRONTEND: "noninteractive"
 
-  # A known good Rust version we should test against.
-  RUST_VERSION_KNOWN: "1.37.0"
+  # A recent version of stable Rust that is known to pass build, test and other
+  # verification steps in this workflow. This was added because using "stable"
+  # could cause some steps to fail.
+  RUST_VERSION_KNOWN: "1.49.0"
 
   # The minimum version of Rust supported.
   RUST_VERSION_MIN: "1.41.1"