Add regression test runner

src/duckstation-regtest/CMakeLists.txt

@@ -0,0 +1,10 @@
+add_executable(duckstation-regtest
+  regtest_host_display.cpp
+  regtest_host_display.h
+  regtest_host_interface.cpp
+  regtest_host_interface.h
+  regtest_settings_interface.cpp
+  regtest_settings_interface.h
+)
+
+target_link_libraries(duckstation-regtest PRIVATE core common frontend-common scmversion)