Remove all cygwin CHOST changes

Since #5448 CHOST defaults to cygwin now, so this
is no longer needed.

ruby/PKGBUILD

@@ -73,11 +73,10 @@ build() {
   mkdir -p ${srcdir}/build-${CHOST} && cd ${srcdir}/build-${CHOST}
 
   export MSYSTEM=CYGWIN
-  local CYGWIN_CHOST="${CHOST/-msys/-cygwin}"
   CFLAGS+=" -fno-strict-aliasing "
   CXXFLAGS+=" -fno-strict-aliasing "
   ../ruby-${pkgver//_/-}/configure \
-    --build=${CYGWIN_CHOST} \
+    --build=${CHOST} \
     --prefix=/usr \
     --exec_prefix=/usr \
     --sysconfdir=/etc \