CMake: only attempt NSIS discovery on Windows

When running CMake with `--warn-uninitialized -Werror=dev`, this prevents the
following:

  CMake Error (dev) at cmake/FindNSIS.cmake:5 (find_program):
    uninitialized variable 'PROGRAMFILES'
  Call Stack (most recent call first):
    cmake/package_info.cmake:30 (find_package)
    CMakeLists.txt:242 (include)

  CMake Error (dev) at cmake/FindNSIS.cmake:5 (find_program):
    uninitialized variable 'ProgramFiles(x86)'
  Call Stack (most recent call first):
    cmake/package_info.cmake:30 (find_package)
    CMakeLists.txt:242 (include)

Gitlab: #2291

diff --git a/cmake/package_info.cmake b/cmake/package_info.cmake
index 070e83441ceb4cc5d1832967d6e0ee40ffe5844d..e1b2a7b176e103be44ccdf51e21161565cf474d7 100644 (file)
--- a/cmake/package_info.cmake
+++ b/cmake/package_info.cmake
@@ -27,7 +27,9 @@ elseif(UNIX)
   endif()
 endif()
 
-find_package(NSIS)
+if(WIN32)
+  find_package(NSIS)
+endif()
 if(NSIS_FOUND)
   set(CPACK_NSIS_MUI_ICON "${CMAKE_SOURCE_DIR}/windows/build/Graphviz.ico")
   set(CPACK_NSIS_MUI_UNIICON "${CMAKE_SOURCE_DIR}/windows/build/Graphviz.ico")