gh-36779: Remove the pycygwin package
    
It was only needed for Cygwin (to handle path conversions), and we're
dropping Cygwin support for real now.

Depends on #36769
    
URL: #36779
Reported by: Michael Orlitzky
Reviewer(s): Dima Pasechnik

Author: Release Manager

build/pkgs/pycygwin/SPKG.rst

@@ -1,4 +1,4 @@
-FORCE $(SCRIPTS) boost_cropped $(BLAS) brial cliquer cypari cysignals cython ecl eclib ecm flint libgd gap giac givaro glpk gmpy2 gsl iml importlib_metadata importlib_resources jupyter_core lcalc lrcalc_python libbraiding libhomfly libpng linbox m4ri m4rie memory_allocator mpc mpfi mpfr $(MP_LIBRARY) ntl numpy pari pip pkgconfig planarity ppl pplpy primesieve primecount primecountpy pycygwin $(PYTHON) requests rw sage_conf singular symmetrica typing_extensions $(PCFILES) | $(PYTHON_TOOLCHAIN) sage_setup $(PYTHON) pythran
+FORCE $(SCRIPTS) boost_cropped $(BLAS) brial cliquer cypari cysignals cython ecl eclib ecm flint libgd gap giac givaro glpk gmpy2 gsl iml importlib_metadata importlib_resources jupyter_core lcalc lrcalc_python libbraiding libhomfly libpng linbox m4ri m4rie memory_allocator mpc mpfi mpfr $(MP_LIBRARY) ntl numpy pari pip pkgconfig planarity ppl pplpy primesieve primecount primecountpy $(PYTHON) requests rw sage_conf singular symmetrica typing_extensions $(PCFILES) | $(PYTHON_TOOLCHAIN) sage_setup $(PYTHON) pythran
 
 ----------
 All lines of this file are ignored except the first.

build/pkgs/pycygwin/checksums.ini

@@ -32,7 +32,6 @@ dnl ... already needed by sage.env
 pkgconfig==esyscmd(`printf $(sed "s/[.]p.*//;" ../pkgconfig/package-version.txt)')
 pplpy==esyscmd(`printf $(sed "s/[.]p.*//;" ../pplpy/package-version.txt)')
 primecountpy==esyscmd(`printf $(sed "s/[.]p.*//;" ../primecountpy/package-version.txt)')
-pycygwin==esyscmd(`printf $(sed "s/[.]p.*//;" ../pycygwin/package-version.txt)'); sys_platform == 'cygwin'
 requests==esyscmd(`printf $(sed "s/[.]p.*//;" ../requests/package-version.txt)')
 typing_extensions==esyscmd(`printf $(sed "s/[.]p.*//;" ../typing_extensions/package-version.txt)')