Copy DLLs to appropriate dir for install-less Windows testing

Co-authored-by: vulcandth <6394873+vulcandth@users.noreply.github.com>

test/CMakeLists.txt

@@ -9,8 +9,15 @@ add_executable(rgbgfx_test gfx/rgbgfx_test.cpp)
 set_target_properties(randtilegen rgbgfx_test PROPERTIES
 # hack for MSVC: no-op generator expression to stop generation of "per-configuration subdirectory"
                       RUNTIME_OUTPUT_DIRECTORY $<1:${CMAKE_CURRENT_SOURCE_DIR}/gfx>)
-target_link_libraries(randtilegen PRIVATE PNG::PNG)
-target_link_libraries(rgbgfx_test PRIVATE PNG::PNG)
+foreach(prog "randtilegen" "rgbgfx_test")
+  target_link_libraries(${prog} PRIVATE PNG::PNG)
+  # Copy the DLLs in the output directory so the program can be run for testing without having to `install`.
+  # From https://cmake.org/cmake/help/v4.3/manual/cmake-generator-expressions.7.html#genex:TARGET_RUNTIME_DLLS.
+  add_custom_command(TARGET ${prog} POST_BUILD COMMENT "Copying ${prog}'s DLLs"
+                     # It would be nice to symlink instead, but that only supports one file at a time.
+                     COMMAND ${CMAKE_COMMAND} -E copy -t $<TARGET_FILE_DIR:${prog}> $<TARGET_RUNTIME_DLLS:${prog}>
+                     COMMAND_EXPAND_LISTS VERBATIM)
+endforeach()
 
 set(ONLY_FREE)
 if(NOT TESTS_RUN_NONFREE)
@@ -31,5 +38,4 @@ configure_file(CTestCustom.cmake.in ${CMAKE_BINARY_DIR}/CTestCustom.cmake @ONLY)
 
 add_test(NAME all
          COMMAND ./run-tests.sh ${ONLY_FREE} ${ONLY_INTERNAL} ${OS_NAME}
-         WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
-)
+         WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR})