Enable `gz log` on Windows

[azeey]

Related to gazebosim/gazebo_test_cases#1554

Environment

• OS Version: All
• Source or binary build? gz-transport14 (8e27a44)
  As pointed out in gz-transport: Logging gazebo_test_cases#1554 (comment), gz log is currently disabled on Windows. See

gz-transport/log/src/CMakeLists.txt

Line 62 in 8e27a44

if(NOT WIN32)

Also related to #247