build: Added a check for NSIS.

cmake/Modules/FindNSIS.cmake

@@ -0,0 +1,31 @@
+# - Try to find NSIS
+# Once done this will define
+#
+#  NSIS_FOUND - system has NSIS
+#  NSIS_MAKE - NSIS creator executable
+#
+#  Copyright (c) 2010 Andreas Schneider <mail@cynapses.org>
+#
+#  Redistribution and use is allowed according to the terms of the New
+#  BSD license.
+#  For details see the accompanying COPYING-CMAKE-SCRIPTS file.
+#
+
+if (NSIS_MAKE)
+  # in cache already
+  set(NSIS_FOUND TRUE)
+elseif (NSIS_MAKE)
+    find_program(NSIS_MAKE
+        NAMES
+            makensis
+        PATHS
+            ${_NSIS_DIR}
+            ${_NSIS_DIR}/Bin
+            $ENV{PROGRAMFILES}/NSIS
+    )
+
+    include(FindPackageHandleStandardArgs)
+    find_package_handle_standard_args(NSIS DEFAULT_MSG NSIS_MAKE)
+
+    mark_as_advanced(NSIS_MAKE)
+endif (NSIS_MAKE)