gtest: Added custom target for all unit tests

Create a target which depends on all unit test executables for ease of
building/running.

Signed-off-by: Noel Eck <noel.eck@intel.com>

tests/unit/CMakeLists.txt

@@ -17,3 +17,11 @@ add_executable(json_tests json/json_tests.cxx)
 target_link_libraries(json_tests GTest::GTest GTest::Main)
 target_include_directories(json_tests PRIVATE "${UPM_COMMON_HEADER_DIRS}/")
 gtest_add_tests(json_tests "" AUTO)
+
+# Add a custom target for unit tests
+add_custom_target(tests-unit ALL
+    DEPENDS
+    utilities_tests
+    json_tests
+    COMMENT "UPM unit test collection")
+