Use CMake MSVC_RUNTIME_LIBRARY to control MSVC flags

CMakeLists.txt

@@ -1,4 +1,6 @@
 cmake_minimum_required(VERSION 3.10 FATAL_ERROR) # because of c++17
+# Set MSVC runtime library flags from CMAKE_MSVC_RUNTIME_LIBRARY
+cmake_policy(SET CMP0091 NEW)
 project(athena)
 if (NOT MSVC)
   set(CMAKE_CXX_STANDARD 20)

atdna/CMakeLists.txt

@@ -10,13 +10,6 @@ get_directory_property(ATDNA_DEFINES COMPILE_DEFINITIONS)
 list(REMOVE_ITEM ATDNA_DEFINES _GLIBCXX_DEBUG=1)
 set_directory_properties(PROPERTIES COMPILE_DEFINITIONS "${ATDNA_DEFINES}")
 
-# Force this binary to /MD flags (to make MSVC happy)
-if(MSVC)
-  set(CMAKE_CXX_FLAGS_DEBUG "/MD /Zi /Ob0 /Od /RTC1")
-  set(CMAKE_CXX_FLAGS_RELWITHDEBINFO "/MD /O2 /Ob2 /DNDEBUG")
-  set(CMAKE_CXX_FLAGS_RELEASE "/MD /Zi /O2 /Ob1 /DNDEBUG")
-endif()
-
 # Find dependencies
 include(FindLLVM.cmake)
 if(NOT LLVM_FOUND)
@@ -147,7 +140,9 @@ set_source_files_properties(main.cpp PROPERTIES COMPILE_DEFINITIONS
 target_include_directories(atdna PRIVATE ${LLVM_INCLUDE_DIRS})
 target_link_directories(atdna PRIVATE ${LLVM_LIBRARY_DIRS})
 if(MSVC)
-  target_compile_options(atdna PRIVATE /GR-)
+  # Allow linking against release-built LLVM libraries
+  target_compile_options(atdna PRIVATE /GR- /D_ITERATOR_DEBUG_LEVEL=0)
+  set_property(TARGET atdna PROPERTY MSVC_RUNTIME_LIBRARY "MultiThreadedDLL")
 else()
   target_compile_options(atdna PRIVATE -fno-rtti -Wno-error)
   set_property(TARGET atdna PROPERTY CXX_STANDARD 17)

extern/zlib/CMakeLists.txt

@@ -1,7 +1,5 @@
-if(NOT WIN32)
 find_package(ZLIB)
-endif()
-if(WIN32 OR NOT ZLIB_FOUND)
+if(NOT ZLIB_FOUND)
 message(STATUS "Using Athena's built-in zlib")
 add_library(z
     adler32.c