Can't compile KataGo with Metal backend

XCode is installed 
```
❯ xcode-select -p
/Applications/Xcode.app/Contents/Developer
```
but I might be missing something as cmake blows up:
```
❯ cmake -G Ninja -DUSE_BACKEND=METAL
CMake Warning:
  No source or binary directory provided.  Both will be assumed to be the
  same as the current working directory, but note that this warning will
  become a fatal error in future CMake releases.


-- The CXX compiler identification is AppleClang 17.0.0.17000013
-- The Swift compiler identification is Apple 6.1
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Check for working Swift compiler: /usr/bin/swiftc
-- Check for working Swift compiler: /usr/bin/swiftc - works
-- Building 'katago' executable for GTP engine and other tools.
-- -DUSE_BACKEND=METAL, using Metal backend.
warning: no such SDK: -print-target-info
error: no input files
CMake Error at external/macos/cmake/modules/InitializeSwift.cmake:42 (string):
  string sub-command JSON failed parsing json string: * Line 1, Column 1

    Syntax error: value, object or array expected.

  .
Call Stack (most recent call first):
  external/macos/cmake/modules/InitializeSwift.cmake:89 (_setup_swift_paths)
  CMakeLists.txt:108 (include)


CMake Error at external/macos/cmake/modules/InitializeSwift.cmake:44 (string):
  string sub-command JSON failed parsing json string: * Line 1, Column 1

    Syntax error: value, object or array expected.

  .
Call Stack (most recent call first):
  external/macos/cmake/modules/InitializeSwift.cmake:89 (_setup_swift_paths)
  CMakeLists.txt:108 (include)


CMake Error at external/macos/cmake/modules/InitializeSwift.cmake:45 (string):
  string sub-command JSON failed parsing json string: * Line 1, Column 1

    Syntax error: value, object or array expected.

  .
Call Stack (most recent call first):
  external/macos/cmake/modules/InitializeSwift.cmake:89 (_setup_swift_paths)
  CMakeLists.txt:108 (include)


CMake Warning (dev) at external/macos/cmake/modules/InitializeSwift.cmake:46 (math):
  Unexpected character in expression at position 1: N

  Unexpected character in expression at position 2: O

  Unexpected character in expression at position 3: T

  Unexpected character in expression at position 4: F

  Unexpected character in expression at position 5: O

  Unexpected character in expression at position 6: U

  Unexpected character in expression at position 7: N

  Unexpected character in expression at position 8: D

Call Stack (most recent call first):
  external/macos/cmake/modules/InitializeSwift.cmake:89 (_setup_swift_paths)
  CMakeLists.txt:108 (include)
This warning is for project developers.  Use -Wno-dev to suppress it.

CMake Error at external/macos/cmake/modules/InitializeSwift.cmake:48 (string):
  string sub-command JSON failed parsing json string: * Line 1, Column 1

    Syntax error: value, object or array expected.

  .
Call Stack (most recent call first):
  external/macos/cmake/modules/InitializeSwift.cmake:89 (_setup_swift_paths)
  CMakeLists.txt:108 (include)


CMake Error at external/macos/cmake/modules/InitializeSwift.cmake:49 (string):
  string sub-command JSON failed parsing json string: * Line 1, Column 1

    Syntax error: value, object or array expected.

  .
Call Stack (most recent call first):
  external/macos/cmake/modules/InitializeSwift.cmake:89 (_setup_swift_paths)
  CMakeLists.txt:108 (include)


CMake Warning (dev) at external/macos/cmake/modules/InitializeSwift.cmake:50 (math):
  Unexpected character in expression at position 1: N

  Unexpected character in expression at position 2: O

  Unexpected character in expression at position 3: T

  Unexpected character in expression at position 4: F

  Unexpected character in expression at position 5: O

  Unexpected character in expression at position 6: U

  Unexpected character in expression at position 7: N

  Unexpected character in expression at position 8: D

Call Stack (most recent call first):
  external/macos/cmake/modules/InitializeSwift.cmake:89 (_setup_swift_paths)
  CMakeLists.txt:108 (include)
This warning is for project developers.  Use -Wno-dev to suppress it.

CMake Error at external/macos/cmake/modules/InitializeSwift.cmake:55 (string):
  string sub-command JSON failed parsing json string: * Line 1, Column 1

    Syntax error: value, object or array expected.

  .
Call Stack (most recent call first):
  external/macos/cmake/modules/InitializeSwift.cmake:89 (_setup_swift_paths)
  CMakeLists.txt:108 (include)


CMake Error at external/macos/cmake/modules/InitializeSwift.cmake:55 (string):
  string sub-command JSON failed parsing json string: * Line 1, Column 1

    Syntax error: value, object or array expected.

  .
Call Stack (most recent call first):
  external/macos/cmake/modules/InitializeSwift.cmake:89 (_setup_swift_paths)
  CMakeLists.txt:108 (include)


CMake Error at external/macos/cmake/modules/InitializeSwift.cmake:60 (string):
  string sub-command JSON failed parsing json string: * Line 1, Column 1

    Syntax error: value, object or array expected.

  .
Call Stack (most recent call first):
  external/macos/cmake/modules/InitializeSwift.cmake:89 (_setup_swift_paths)
  CMakeLists.txt:108 (include)


CMake Error at external/macos/cmake/modules/InitializeSwift.cmake:60 (string):
  string sub-command JSON failed parsing json string: * Line 1, Column 1

    Syntax error: value, object or array expected.

  .
Call Stack (most recent call first):
  external/macos/cmake/modules/InitializeSwift.cmake:89 (_setup_swift_paths)
  CMakeLists.txt:108 (include)


-- Including Git revision in the compiled executable, specify -DNO_GIT_REVISION=1 to disable
-- Found Git: /usr/bin/git (found version "2.39.5 (Apple Git-154)")
-- Found ZLIB: /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/lib/libz.tbd (found version "1.2.12")
-- Setting up build for GNU or Clang.
-- ARM architecture detected: adding -fsigned-char flag
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD - Success
-- Found Threads: TRUE
-- Enabling AppleClang-specific build options.
-- Configuring incomplete, errors occurred!
```
Any ideas?

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