xz not present in OS X yet; also fix build report naming

.travis.yml

@@ -58,12 +58,12 @@ before_script:
     (
       set -e
       if test osx = "${TRAVIS_OS_NAME}" && test -n "${TRAVIS_TAG}"; then
-        rm -rf macosx/build-report macosx/build-report.txz
+        rm -rf macosx/build-report macosx/build-report.tgz
         mkdir macosx/build-report
         cd macosx/build-report
         ../brew-deps.sh describe
         ../osx-xcode.sh describe
-        tar -cf - . | xz > ../build-report.txz
+        tar -czf ../build-report.tgz .
       fi
     )
 
@@ -92,7 +92,7 @@ deploy:
   skip_cleanup: true
   # Using a shell variable in deploy.file is undocumented but seems to work.
   file: macosx/${TRAVIS_TAG}.pkg
-  file: macosx/build-report.pkg
+  file: macosx/build-report.tgz
   on:
     repo: cgull/mosh
     tags: true