Run tests with TSAN where available, add macOS CI for Swift 5.2

Motivation:

We should run TSAN in tests.

Modifications:

- run TSAN by default; don't run TSAN for Swift 5.0 on Linux
- add Xcode 11.4 to add CI for Swift 5.2 on macOS

Result:

Resolves grpc#757

.travis-script.sh

@@ -46,8 +46,15 @@ make_all() {
 
 make_test() {
   echo -en 'travis_fold:start:make.test\\r'
-  info "Running Swift tests"
-  make test
+
+  if [[ ${NO_TSAN} == "true" ]]; then
+    info "Running Swift tests"
+    make test
+  else
+    info "Running Swift tests with TSAN"
+    make test-tsan
+  fi
+
   success "Swift tests passed"
   echo -en 'travis_fold:end:make.test\\r'
 }

.travis.yml

@@ -31,7 +31,11 @@ jobs:
       env: RUN_INTEROP_TESTS=false SWIFT_VERSION=5.1.5
     - <<: *tests
       name: "Unit Tests: Ubuntu 18.04 (Swift 5.0)"
-      env: RUN_INTEROP_TESTS=false SWIFT_VERSION=5.0.3
+      env: RUN_INTEROP_TESTS=false SWIFT_VERSION=5.0.3 NO_TSAN=true
+    - <<: *tests
+      name: "Unit Tests: Xcode 11.4 (Swift 5.2)"
+      os: osx
+      osx_image: xcode11.4
     - <<: *tests
       name: "Unit Tests: Xcode 11.3 (Swift 5.1)"
       os: osx
@@ -55,6 +59,10 @@ jobs:
     - <<: *interop_tests
       name: "Interoperability Tests: Ubuntu 18.04 (Swift 5.0)"
       env: RUN_INTEROP_TESTS=true SWIFT_VERSION=5.0.3
+    - <<: *interop_tests
+      name: "Interoperability Tests: Xcode 11.4 (Swift 5.2)"
+      os: osx
+      osx_image: xcode11.4
     - <<: *interop_tests
       name: "Interoperability Tests: Xcode 11.3 (Swift 5.1)"
       os: osx

Makefile

@@ -101,6 +101,11 @@ generate-route-guide: ${ROUTE_GUIDE_PB} ${ROUTE_GUIDE_GRPC}
 test:
 	${SWIFT_TEST}
 
+# Normal test suite with TSAN enabled.
+.PHONY:
+test-tsan:
+	${SWIFT_TEST} --sanitize=thread
+
 # Checks that linuxmain has been updated: requires macOS.
 .PHONY:
 test-generate-linuxmain: generate-linuxmain