Merge #1227 #1228

1227: Test on Rust stable again r=asomers a=asomers

This commit reverts eba3b51, which
worked around a Travis CI bug that has since been fixed.  The effect is
to resume testing on the latest Rust stable.

1228: Fix an "unused macro" warning on non-Linux platforms r=asomers a=asomers

cc @glebpom 

Co-authored-by: Alan Somers <asomers@gmail.com>

.travis.yml

@@ -85,12 +85,8 @@ matrix:
       rust: 1.36.0
 
     # Make sure stable is always working too
-    # FIXME: Travis's "stable" images are stuck on 1.35.0.  Until that's fixed,
-    # explicitly request 1.37.0, which is as of this writing the latest stable
-    # release.
-    # https://travis-ci.community/t/stable-rust-channel-outdated/4213
     - env: TARGET=x86_64-unknown-linux-gnu
-      rust: 1.37.0
+      rust: stable
 
     # Test that we can build with the lowest version of all dependencies.
     # "cargo test" doesn't work because some of our dev-dependencies, like

test/test.rs

@@ -102,7 +102,7 @@ cfg_if! {
 }
 
 cfg_if! {
-    if #[cfg(any(target_os = "android", target_os = "linux"))] {
+    if #[cfg(target_os = "linux")] {
         macro_rules! require_kernel_version {
             ($name:expr, $version_requirement:expr) => {
                 use ::std::io::Write;
@@ -130,10 +130,6 @@ cfg_if! {
                 }
             }
         }
-    } else {
-        macro_rules! require_kernel_version {
-            ($name:expr) => {}
-        }
     }
 }