CMake: Add SPDLOG_STATIC_VCRT to choose static MSVC runtime

CMakeLists.txt

@@ -2,6 +2,8 @@
 
 cmake_minimum_required(VERSION 3.10)
 
+cmake_policy(SET CMP0091 NEW)
+
 # ---------------------------------------------------------------------------------------
 # Start spdlog project
 # ---------------------------------------------------------------------------------------
@@ -87,6 +89,7 @@ endif()
 if(WIN32)
     option(SPDLOG_WCHAR_SUPPORT "Support wchar api" OFF)
     option(SPDLOG_WCHAR_FILENAMES "Support wchar filenames" OFF)
+    option(SPDLOG_STATIC_VCRT "Force /MT for static VC runtimes" OFF)
 endif()
 if(${CMAKE_SYSTEM_NAME} STREQUAL "Linux")
     option(SPDLOG_CLOCK_COARSE
@@ -124,6 +127,10 @@ if(NOT SPDLOG_FMT_EXTERNAL AND NOT SPDLOG_FMT_EXTERNAL_HO)
     list(APPEND SPDLOG_SRCS src/fmt.cpp)
 endif()
 
+if(MSVC AND SPDLOG_STATIC_VCRT)
+    set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreaded$<$<CONFIG:Debug>:Debug>")
+endif()
+
 if(SPDLOG_BUILD_SHARED OR BUILD_SHARED_LIBS)
     if(WIN32)
         configure_file(${CMAKE_CURRENT_SOURCE_DIR}/cmake/version.rc.in ${CMAKE_CURRENT_BINARY_DIR}/version.rc @ONLY)