WAF build problem (cygwin)

Mike@Mike /cygdrive/h/__ARDU/ardupilot
$ ./waf sub -vv
Waf: Entering directory `/cygdrive/h/__ARDU/ardupilot/build/px4-v2'
21:10:33 runner ['/usr/bin/git', 'rev-parse', '--short=8', 'HEAD']
21:10:33 runner ['/usr/bin/git', 'rev-parse', '--short=8', 'HEAD']
21:10:33 runner ['/usr/bin/git', 'rev-parse', '--short=8', 'HEAD']
21:10:35 runner ('/usr/bin/git', 'submodule', 'status', '--recursive', '--', '/cygdrive/h/__ARDU/ardupilot/modules/PX4Firmware')
21:10:37 runner ('/usr/bin/git', 'submodule', 'status', '--recursive', '--', '/cygdrive/h/__ARDU/ardupilot/modules/PX4NuttX')
21:10:38 runner ('/usr/bin/git', 'submodule', 'status', '--recursive', '--', '/cygdrive/h/__ARDU/ardupilot/modules/uavcan')
21:10:39 runner ('/usr/bin/git', 'submodule', 'status', '--recursive', '--', '/cygdrive/h/__ARDU/ardupilot/modules/mavlink')
[ 8/14] CMake Configure px4
21:10:40 runner ['/cygdrive/c/Program Files/CMake/bin/cmake', '-Wno-deprecated', '/cygdrive/h/__ARDU/ardupilot/modules/PX4Firmware', "-DARDUPILOT_BUILD='YES'", "-DCMAKE_MODULE_PATH='/cygdrive/h/__ARDU/ardupilot/Tools/ardupilotwaf/px4/cmake'", "-DCONFIG='nuttx_px4fmu-v2_apm'", "-DEXTRA_CXX_FLAGS='-Wno-error=double-promotion -Wno-error=reorder -DCMAKE_BUILD -DARDUPILOT_BUILD -I/cygdrive/h/__ARDU/ardupilot/build/px4-v2/libraries/GCS_MAVLink -I/cygdrive/h/__ARDU/ardupilot/build/px4-v2/libraries/GCS_MAVLink/include/mavlink -Wl,--gc-sections'", "-DEXTRA_C_FLAGS='-DCMAKE_BUILD'", "-DNUTTX_SRC='/cygdrive/h/__ARDU/ardupilot/modules/PX4NuttX'", "-DPX4_NUTTX_ROMFS='/cygdrive/h/__ARDU/ardupilot/build/px4-v2/px4-extra-files/ROMFS'", '-GUnix Makefiles']
CMake Error: The source directory "/cygdrive/h/__ARDU/ardupilot/modules/PX4Firmware" does not exist.
Specify --help for usage, or press the help button on the CMake GUI.

Waf: Leaving directory `/cygdrive/h/__ARDU/ardupilot/build/px4-v2'
  File "/cygdrive/h/__ARDU/ardupilot/modules/waf/waf-light", line 167, in <module>
    Scripting.waf_entry_point(cwd, VERSION, wafdir)
  File "/cygdrive/h/__ARDU/ardupilot/modules/waf/waflib/Scripting.py", line 165, in waf_entry_point
    run_commands()
  File "/cygdrive/h/__ARDU/ardupilot/modules/waf/waflib/Scripting.py", line 266, in run_commands
    ctx = run_command(cmd_name)
  File "/cygdrive/h/__ARDU/ardupilot/modules/waf/waflib/Scripting.py", line 250, in run_command
    ctx.execute()
  File "/cygdrive/h/__ARDU/ardupilot/modules/waf/waflib/Scripting.py", line 616, in execute
    return execute_method(self)
  File "/cygdrive/h/__ARDU/ardupilot/modules/waf/waflib/Build.py", line 255, in execute
    self.execute_build()
  File "/cygdrive/h/__ARDU/ardupilot/modules/waf/waflib/Build.py", line 275, in execute_build
    self.compile()
  File "/cygdrive/h/__ARDU/ardupilot/modules/waf/waflib/Tools/errcheck.py", line 175, in check_compile
    ret = self.orig_compile()
  File "/cygdrive/h/__ARDU/ardupilot/modules/waf/waflib/Build.py", line 377, in compile
    raise Errors.BuildError(self.producer.error)
  File "/cygdrive/h/__ARDU/ardupilot/modules/waf/waflib/Errors.py", line 45, in __init__
    WafError.__init__(self, self.format_error())

Build failed
-> missing file: '/cygdrive/h/__ARDU/ardupilot/build/px4-v2/modules/PX4Firmware/CMakeCache.txt'

Mike@Mike /cygdrive/h/__ARDU/ardupilot
$ ls /cygdrive/h/__ARDU/ardupilot/modules/PX4Firmware/
cmake            Debug                     Images            LICENSE.md     makefiles  msg            posix-configs  src                 Tools
CMakeLists.txt   Documentation             integrationtests  Makefile       mavlink    nuttx-configs  README.md      template_.cproject  unittests
CONTRIBUTING.md  Firmware.sublime-project  launch            Makefile.make  misc       package.xml    ROMFS          template_.project   Vagrantfile

Mike@Mike /cygdrive/h/__ARDU/ardupilot
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