cmake: add prefixed cpack and CPACK_NSIS_EXECUTABLE

see #1502

src/cmake-1-fixes.patch

@@ -30,7 +30,6 @@ see also:
 https://gitlab.kitware.com/cmake/cmake/issues/16291
 https://gitlab.kitware.com/cmake/cmake/issues/16919
 
-
 diff --git a/Modules/Compiler/GNU.cmake b/Modules/Compiler/GNU.cmake
 index 1111111..2222222 100644
 --- a/Modules/Compiler/GNU.cmake
@@ -44,3 +43,25 @@ index 1111111..2222222 100644
      set(CMAKE_INCLUDE_SYSTEM_FLAG_${lang} "-isystem ")
    endif()
  endmacro()
+
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Tony Theodore <tonyt@logyst.com>
+Date: Tue, 15 Aug 2017 15:25:06 +1000
+Subject: [PATCH] add CPACK_NSIS_EXECUTABLE variable
+
+
+diff --git a/Source/CPack/cmCPackNSISGenerator.cxx b/Source/CPack/cmCPackNSISGenerator.cxx
+index 1111111..2222222 100644
+--- a/Source/CPack/cmCPackNSISGenerator.cxx
++++ b/Source/CPack/cmCPackNSISGenerator.cxx
+@@ -384,7 +384,9 @@ int cmCPackNSISGenerator::InitializeInternal()
+   }
+ #endif
+ 
+-  nsisPath = cmSystemTools::FindProgram("makensis", path, false);
++  this->SetOptionIfNotSet("CPACK_NSIS_EXECUTABLE", "makensis");
++  nsisPath = cmSystemTools::FindProgram(
++    this->GetOption("CPACK_NSIS_EXECUTABLE"), path, false);
+ 
+   if (nsisPath.empty()) {
+     cmCPackLogger(

src/cmake-conf.mk

@@ -36,6 +36,8 @@ define $(PKG)_BUILD
         -DINPUT='$(PWD)/src/cmake/conf/target-cmake.in' \
         -DOUTPUT='$(PREFIX)/bin/$(TARGET)-cmake'
     chmod 0755 '$(PREFIX)/bin/$(TARGET)-cmake'
+
+    ln -sf '$(PREFIX)/$(BUILD)/bin/cpack' '$(PREFIX)/bin/$(TARGET)-cpack'
 endef
 
 define $(PKG)_BUILD_$(BUILD)

src/cmake/conf/mxe-conf.cmake.in

@@ -56,6 +56,7 @@ set(CMAKE_Fortran_COMPILER @PREFIX@/bin/@TARGET@-gfortran)
 set(CMAKE_RC_COMPILER @PREFIX@/bin/@TARGET@-windres)
 # CMAKE_RC_COMPILE_OBJECT is defined in:
 #     <cmake root>/share/cmake-X.Y/Modules/Platform/Windows-windres.cmake
+set(CPACK_NSIS_EXECUTABLE @TARGET@-makensis)
 
 ## Individual package configuration
 file(GLOB mxe_cmake_files