Only run clippy and rustfmt on CI if the component is available

.travis.yml

@@ -129,16 +129,19 @@ matrix:
     - name: "rustfmt"
       install: true
       rust: nightly
-      before_script: rustup component add rustfmt-preview
-      script: cargo fmt --all -- --check
+      script: |
+        if rustup component add rustfmt-preview ; then
+            cargo fmt --all -- --check
+        fi
     - name: "clippy"
       install: true
       rust: nightly
       # allow(clippy::all) fails in the syscrate, so we can't use --all here:
       script: |
-        if rustup component add clippy-preview; then
+        if rustup component add clippy-preview ; then
             cargo clippy -p jemalloc-sys -- -D clippy::pedantic
             cargo clippy -p jemallocator -- -D clippy::pedantic
+            cargo clippy -p jemallocator-global -- -D clippy::pedantic
             cargo clippy -p jemalloc-ctl -- -D clippy::pedantic
         fi
     - name: "Shellcheck"