iOS: CMake 3.17 crash on missing per-architecture sysroots

after upgrade to cmake 3.17. any generator except xcode with -DCMAKE_SYSTEM_NAME=iOS will crash.

cmake .. -DCMAKE_SYSTEM_NAME=iOS "-DCMAKE_OSX_ARCHITECTURES=armv7;armv7s;arm64;i386;x86_64" -DCMAKE_OSX_DEPLOYMENT_TARGET=9.3
CMake Warning at cmake-3.17.0-Darwin-x86_64/CMake.app/Contents/share/cmake-3.17/Modules/Platform/Darwin-Initialize.cmake:204 (message):
  No SDK found for architecture 'armv7'
Call Stack (most recent call first):
  cmake-3.17.0-Darwin-x86_64/CMake.app/Contents/share/cmake-3.17/Modules/Platform/Darwin-Initialize.cmake:213 (_apple_resolve_multi_arch_sysroots)
  cmake-3.17.0-Darwin-x86_64/CMake.app/Contents/share/cmake-3.17/Modules/Platform/iOS-Initialize.cmake:1 (include)
  cmake-3.17.0-Darwin-x86_64/CMake.app/Contents/share/cmake-3.17/Modules/CMakeSystemSpecificInitialize.cmake:21 (include)
  CMakeLists.txt:2 (project)


CMake Warning at cmake-3.17.0-Darwin-x86_64/CMake.app/Contents/share/cmake-3.17/Modules/Platform/Darwin-Initialize.cmake:204 (message):
  No SDK found for architecture 'armv7s'
Call Stack (most recent call first):
  cmake-3.17.0-Darwin-x86_64/CMake.app/Contents/share/cmake-3.17/Modules/Platform/Darwin-Initialize.cmake:213 (_apple_resolve_multi_arch_sysroots)
  cmake-3.17.0-Darwin-x86_64/CMake.app/Contents/share/cmake-3.17/Modules/Platform/iOS-Initialize.cmake:1 (include)
  cmake-3.17.0-Darwin-x86_64/CMake.app/Contents/share/cmake-3.17/Modules/CMakeSystemSpecificInitialize.cmake:21 (include)
  CMakeLists.txt:2 (project)


CMake Warning at cmake-3.17.0-Darwin-x86_64/CMake.app/Contents/share/cmake-3.17/Modules/Platform/Darwin-Initialize.cmake:204 (message):
  No SDK found for architecture 'i386'
Call Stack (most recent call first):
  cmake-3.17.0-Darwin-x86_64/CMake.app/Contents/share/cmake-3.17/Modules/Platform/Darwin-Initialize.cmake:213 (_apple_resolve_multi_arch_sysroots)
  cmake-3.17.0-Darwin-x86_64/CMake.app/Contents/share/cmake-3.17/Modules/Platform/iOS-Initialize.cmake:1 (include)
  cmake-3.17.0-Darwin-x86_64/CMake.app/Contents/share/cmake-3.17/Modules/CMakeSystemSpecificInitialize.cmake:21 (include)
  CMakeLists.txt:2 (project)


-- The C compiler identification is AppleClang 11.0.3.11030032
-- The CXX compiler identification is AppleClang 11.0.3.11030032
-- Check for working C compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/cc
cmake(65662,0x10ef1adc0) malloc: can't allocate region
:*** mach_vm_map(size=8459008377403949056, flags: 60000100) failed (error code=3)
cmake(65662,0x10ef1adc0) malloc: *** set a breakpoint in malloc_error_break to debug
libc++abi.dylib: terminating with uncaught exception of type std::bad_alloc: std::bad_alloc
[1]    65662 abort      ../cmake-3.17.0-Darwin-x86_64/CMake.app/Contents/bin/cmake ..