From c3340c994a47ef7df5945e2e731319fc2c1f3ef8 Mon Sep 17 00:00:00 2001
From: Ben RUBSON <ben.rubson@gmail.com>
Date: Wed, 25 Apr 2018 09:30:49 +0200
Subject: [PATCH] Cygwin, set proper installation prefix, but don't force
 (#513)

---
 CMakeLists.txt | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index cc6a0d4..5509c86 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -36,7 +36,9 @@ if (NOT DEFINED LIB_INSTALL_DIR)
 endif ()
 
 if (CYGWIN)
-  set (CMAKE_INSTALL_PREFIX /usr)
+  if (CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT)
+    set (CMAKE_INSTALL_PREFIX /usr)
+  endif()
 endif()
 
 # We need C++ 11