depends: add CMAKE_SYSTEM_VERSION to toolchain file, set minimum Windows version

contrib/depends/Makefile

@@ -152,6 +152,7 @@ $(host_prefix)/share/toolchain.cmake : toolchain.cmake.in $(host_prefix)/.stamp_
             -e 's|@release_type@|$(cmake_release_type)|' \
             -e 's|@build_tests@|$(build_tests)|' \
             -e 's|@cmake_system_name@|$($(host_os)_cmake_system)|' \
+            -e 's|@cmake_system_version@|$($(host_os)_cmake_system_version)|' \
             -e 's|@prefix@|$($(host_arch)_$(host_os)_prefix)|'\
             -e 's|@arch@|$(host_arch)|'\
             $< > $@

contrib/depends/funcs.mk

@@ -200,6 +200,9 @@ ifneq ($(host),$(build))
 $(1)_cmake += -DCMAKE_SYSTEM_NAME=$($(host_os)_cmake_system)
 $(1)_cmake += -DCMAKE_C_COMPILER_TARGET=$(host)
 $(1)_cmake += -DCMAKE_CXX_COMPILER_TARGET=$(host)
+ifneq ($($(host_os)_cmake_system_version),)
+$(1)_cmake += -DCMAKE_SYSTEM_VERSION=$($(host_os)_cmake_system_version)
+endif
 endif
 endif
 endef

contrib/depends/hosts/mingw32.mk

@@ -11,3 +11,4 @@ mingw32_debug_CXXFLAGS=$(mingw32_debug_CFLAGS)
 mingw32_debug_CPPFLAGS=-D_GLIBCXX_DEBUG -D_GLIBCXX_DEBUG_PEDANTIC
 
 mingw32_cmake_system=Windows
+mingw32_cmake_system_version=10.0

contrib/depends/packages/unbound.mk

@@ -15,7 +15,6 @@ define $(package)_set_vars
   $(package)_config_opts_w64=--enable-static-exe --sysconfdir=/etc --prefix=$(host_prefix) --target=$(host_prefix)
   $(package)_config_opts_x86_64_darwin=ac_cv_func_SHA384_Init=yes
   $(package)_build_opts_mingw32=LDFLAGS="$($(package)_ldflags) -lpthread"
-  $(package)_cflags_mingw32+="-D_WIN32_WINNT=0x600"
 endef
 
 define $(package)_preprocess_cmds

contrib/depends/toolchain.cmake.in

@@ -1,5 +1,6 @@
 # Set the system name to one of Android, Darwin, FreeBSD, Linux, or Windows
 SET(CMAKE_SYSTEM_NAME @cmake_system_name@)
+SET(CMAKE_SYSTEM_VERSION @cmake_system_version@)
 SET(CMAKE_SYSTEM_PROCESSOR @arch@)
 SET(CMAKE_BUILD_TYPE @release_type@)