Only compile ports/servo on Linux

.travis.yml

@@ -23,7 +23,7 @@ matrix:
       script:
          # see https://github.com/servo/servo/issues/20664
          #- ./mach cargo check -p compositing --no-default-features
-         - ./mach build -d --verbose
+         - ./mach build -d --verbose -p servo
          - ./mach test-unit
          - ./mach clean
          - bash etc/ci/lockfile_changed.sh

etc/ci/buildbot_steps.yml

@@ -73,14 +73,14 @@ linux-rel-intermittent:
   - ./mach clean-nightlies --keep 3 --force
   - ./mach clean-cargo-cache --keep 3 --force
   - ./etc/ci/clean_build_artifacts.sh
-  - ./mach build --release
+  - ./mach build --release -p servo
   - ./etc/ci/check_intermittents.sh --log-raw intermittents.log
 
 linux-rel-nogate:
   - ./mach clean-nightlies --keep 3 --force
   - ./mach clean-cargo-cache --keep 3 --force
   - ./etc/ci/clean_build_artifacts.sh
-  - ./mach build --release
+  - ./mach build --release -p servo
   - python ./etc/ci/chaos_monkey_test.py
   - env RUSTFLAGS= bash ./etc/ci/mutation_test.sh
 
@@ -100,11 +100,11 @@ linux-dev:
     - ./etc/ci/clean_build_artifacts.sh
     - ./mach test-tidy --no-progress --all
     - ./mach test-tidy --no-progress --self-test
-    - ./mach build --dev
+    - ./mach build --dev -p servo
     - ./mach test-unit
     - python ./etc/memory_reports_over_time.py --test
     - ./mach package --dev
-    - ./mach build --dev --no-default-features --features default-except-unstable
+    - ./mach build --dev --no-default-features --features default-except-unstable -p servo
     - bash ./etc/ci/lockfile_changed.sh
     - bash ./etc/ci/check_no_panic.sh
     - ./etc/ci/clean_build_artifacts.sh
@@ -117,7 +117,7 @@ linux-rel-wpt:
     - ./mach clean-nightlies --keep 3 --force
     - ./mach clean-cargo-cache --keep 3 --force
     - ./etc/ci/clean_build_artifacts.sh
-    - ./mach build --release --with-debug-assertions
+    - ./mach build --release --with-debug-assertions -p servo
     - ./mach test-wpt-failure
     - ./mach test-wpt --release --processes 24 --total-chunks 2 --this-chunk 1 --log-raw test-wpt.log --log-errorsummary wpt-errorsummary.log --always-succeed
     - ./mach filter-intermittents wpt-errorsummary.log --log-intermittents intermittents.log --log-filteredsummary filtered-wpt-errorsummary.log --tracker-api default --reporter-api default
@@ -131,7 +131,7 @@ linux-rel-css:
     - ./mach clean-nightlies --keep 3 --force
     - ./mach clean-cargo-cache --keep 3 --force
     - ./etc/ci/clean_build_artifacts.sh
-    - ./mach build --release --with-debug-assertions
+    - ./mach build --release --with-debug-assertions -p servo
     - ./mach test-wpt --release --processes 24 --total-chunks 2 --this-chunk 2 --log-raw test-wpt.log --log-errorsummary wpt-errorsummary.log --always-succeed
     - ./mach filter-intermittents wpt-errorsummary.log --log-intermittents intermittents.log --log-filteredsummary filtered-wpt-errorsummary.log --tracker-api default --reporter-api default
     - bash ./etc/ci/lockfile_changed.sh
@@ -141,7 +141,7 @@ linux-nightly:
   - ./mach clean-nightlies --keep 3 --force
   - ./mach clean-cargo-cache --keep 3 --force
   - ./etc/ci/clean_build_artifacts.sh
-  - ./mach build --release
+  - ./mach build --release -p servo
   - ./mach package --release
   - ./mach upload-nightly linux
   - ./mach test-perf