Remove all cygwin CHOST changes

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

diffutils/PKGBUILD

@@ -25,9 +25,8 @@ build() {
   # make sure tests are running OK
   sed -i "s/mkdir -m 0700/mkdir /" tests/init.sh
 
-  local CYGWIN_CHOST="${CHOST/-msys/-cygwin}"
   ./configure \
-    --build=${CYGWIN_CHOST} \
+    --build=${CHOST} \
     --prefix=/usr \
     --without-libiconv-prefix \
     --without-libintl-prefix