qt5: fix header_module variable typo

pkgs/development/libraries/qt-5/5.12/qtbase.patch.d/0012-fix-header_module.patch

@@ -1,4 +1,4 @@
-From 7abf00d01ed0a3099cb2f5950c7ebc57a3960094 Mon Sep 17 00:00:00 2001
+From 821db0c3056a813e2d0d36fbb2c7361df5559b05 Mon Sep 17 00:00:00 2001
 From: Will Dietz <w@wdtz.org>
 Date: Mon, 30 Sep 2019 20:15:40 -0500
 Subject: [PATCH 12/12] fix header_module
@@ -8,7 +8,7 @@ Subject: [PATCH 12/12] fix header_module
  1 file changed, 1 insertion(+), 1 deletion(-)
 
 diff --git a/mkspecs/features/qt_module.prf b/mkspecs/features/qt_module.prf
-index 9015b30d73..351a46227f 100644
+index 9015b30d73..7347c791b4 100644
 --- a/mkspecs/features/qt_module.prf
 +++ b/mkspecs/features/qt_module.prf
 @@ -84,7 +84,7 @@ header_module {
@@ -16,7 +16,7 @@ index 9015b30d73..351a46227f 100644
  
      # Allow creation of .prl, .la and .pc files.
 -    target.path = $$[QT_INSTALL_LIBS]
-+    target.path = $$NIXOS_OUTPUT_OUT/lib
++    target.path = $$NIX_OUTPUT_OUT/lib
      target.CONFIG += dummy_install
      INSTALLS    += target
  } else {