For CI - avoid GNU option for 'xargs' that is not supported on Mac.

Just silently perform the commands without sending anything to error stream.

Rakefile

@@ -309,12 +309,7 @@ task :ci do
     system 'clang --version && emcc --version' or abort 'Failed to find Emscripten compiler toolchain'
   end
   # Show CMake version
-  if ENV['ANDROID']
-    # Android build uses SDK's embedded CMake which is non-vanilla version of CMake
-    system '$ANDROID_HOME/cmake/*/bin/cmake --version' or abort 'Failed to find CMake'
-  else
-    system 'cmake --version' or abort 'Failed to find CMake'
-  end
+  system 'cmake --version' or abort 'Failed to find CMake'
   puts; $stdout.flush
   # Use out-of-source build tree
   ENV['build_tree'] = 'build/ci'
@@ -323,7 +318,7 @@ task :ci do
   # When not explicitly specified then use generic generator
   generator = ENV['XCODE'] ? 'xcode' : (ENV['APPVEYOR'] ? (ENV['MINGW'] ? 'mingw' : 'vs2019') : '')
   # Cache the initial build tree for next run on platform that is slow to generate the build tree
-  system "mkdir -p #{ENV['build_tree']} && cp -rp #{ENV['HOME']}/initial-build-tree/* #{ENV['build_tree']} && git diff $(cat #{ENV['HOME']}/initial-build-tree/.sha1) $TRAVIS_COMMIT --name-only |grep -i cmake |xargs -r touch" if (ENV['OSX'] || ENV['WEB']) && ENV['CI'] && File.exist?("#{ENV['HOME']}/initial-build-tree/.sha1")
+  system "mkdir -p #{ENV['build_tree']} && cp -rp #{ENV['HOME']}/initial-build-tree/* #{ENV['build_tree']} && git diff $(cat #{ENV['HOME']}/initial-build-tree/.sha1) $TRAVIS_COMMIT --name-only 2>/dev/null |grep -i cmake |xargs touch 2>/dev/null" if (ENV['OSX'] || ENV['WEB']) && ENV['CI'] && File.exist?("#{ENV['HOME']}/initial-build-tree/.sha1")
   system "rake cmake #{generator} URHO3D_DATABASE_SQLITE=1 URHO3D_EXTRAS=1" or abort 'Failed to configure Urho3D library build'
   system "bash -c 'cp -rp #{ENV['build_tree']}/* #{ENV['HOME']}/initial-build-tree 2>/dev/null && rm -rf #{ENV['HOME']}/initial-build-tree/{bin,include} 2>/dev/null && echo $TRAVIS_COMMIT >#{ENV['HOME']}/initial-build-tree/.sha1'" if (ENV['OSX'] || ENV['WEB']) && ENV['CI']
   next if timeup    # Measure the CMake configuration overhead