Build system: delete half-baked Cygwin support

We only support building GHC on mys2 nowadays, see
https://ghc.haskell.org/trac/ghc/wiki/Building/Preparation/Windows.

This (partially) reverts various commits from a few years ago, among which:
  * 5775d5142da227d65fb86994d363eb16841ee642
    "Add OSTYPE build-system variable, and use it"
  * 3fb8c431824aa2f3bd979e35d1a283546fcfbe74
    "Fix building libgmp on cygwin"
  * cdbb4720c424500adb57cbbef69721d0b039fa46
    "Fix cmd invocation by libffi cuild system on Windows 7 cygwin"
  * e8121501ee3549a35e954726ccfd871ac9d51f83
    "Fix dblatex and xml* tool detection on Windows"

Reviewed by: austin, Phyx

Differential Revision: https://phabricator.haskell.org/D1155

1 files changed, 0 insertions, 4 deletions

diff --git a/validate b/validate
index 39e1f01120..5f24e19bd1 100755
--- a/validate
+++ b/validate
@@ -163,10 +163,6 @@ if [ $no_clean -eq 0 ]; then
     $make maintainer-clean NO_CLEAN_GMP=YES
 
     INSTDIR=`pwd`/inst
-    if [ "$OSTYPE" = "cygwin" ]
-    then
-        INSTDIR=`cygpath -m "$INSTDIR"`
-    fi
 
     if [ $use_dph -eq 1 ]; then
         perl -w boot --validate --required-tag=dph