Travis: Disable the Rust macOS build

This build was added in 0.3.5.

We need to mitigate slow scheduling of Travis macOS jobs.

Closes ticket 32177.

.travis.yml

@@ -53,9 +53,10 @@ matrix:
     ## We check disable module dirauth
     - env: MODULES_OPTIONS="--disable-module-dirauth"
     ## We run rust on macOS, because we have seen macOS rust failures before
-    - env: RUST_OPTIONS="--enable-rust --enable-cargo-online-mode"
-      compiler: clang
-      os: osx
+    # Disabled due to slow Travis macOS builds, see #32177
+    #- env: RUST_OPTIONS="--enable-rust --enable-cargo-online-mode"
+    #  compiler: clang
+    #  os: osx
     ## We run chutney on macOS, because macOS Travis has IPv6
     # Disabled due to slow Travis macOS builds, see #32177
     #- env: CHUTNEY="yes" CHUTNEY_ALLOW_FAILURES="2" SKIP_MAKE_CHECK="yes"