Tests: Set PCSX2_CORE macro

They shouldn't be using wx, and it gets rid of the pthreads4w reference.

tests/ctest/CMakeLists.txt

@@ -63,6 +63,7 @@ add_custom_command(TARGET unittests POST_BUILD COMMAND ${CMAKE_CTEST_COMMAND})
 macro(add_pcsx2_test target)
 	add_executable(${target} EXCLUDE_FROM_ALL ${ARGN})
 	target_link_libraries(${target} PRIVATE gtest_main common)
+	target_compile_definitions(${target} PRIVATE "PCSX2_CORE")
 	add_dependencies(unittests ${target})
 	add_test(NAME ${target} COMMAND ${target})
 endmacro()