chore: Add cmake flag to disable unit tests.

CMakeLists.txt

@@ -146,6 +146,8 @@ endif()
 option(BUILD_MISC_TESTS "Build additional tests" OFF)
 option(BUILD_FUN_UTILS "Build additional just for fun utilities" OFF)
 
+option(UNITTEST "Enable unit tests (disable if you don't have a working gmock or gtest)" ON)
+
 option(AUTOTEST "Enable autotests (mainly for CI)" OFF)
 if(AUTOTEST)
   option(NON_HERMETIC_TESTS "Whether to build and run tests that depend on an internet connection" OFF)
@@ -534,7 +536,7 @@ endfunction()
 
 # The actual unit tests follow.
 #
-if(TARGET GTest::gtest AND TARGET GTest::gmock)
+if(UNITTEST AND TARGET GTest::gtest AND TARGET GTest::gmock)
   unit_test(toxav ring_buffer)
   unit_test(toxav rtp)
   unit_test(toxcore DHT)