fix ncurses pkgconfig path a final time

pkgs/development/libraries/ncurses/default.nix

@@ -30,7 +30,10 @@ stdenv.mkDerivation rec {
 
   buildInputs = lib.optional (mouseSupport && stdenv.isLinux) gpm;
 
-  preConfigure = lib.optionalString stdenv.isCygwin ''
+  preConfigure = ''
+    export PKG_CONFIG_LIBDIR="$out/lib/pkgconfig"
+    mkdir -p "$PKG_CONFIG_LIBDIR"
+  '' + lib.optionalString stdenv.isCygwin ''
     sed -i -e 's,LIB_SUFFIX="t,LIB_SUFFIX=",' configure
   '';
 
@@ -40,11 +43,6 @@ stdenv.mkDerivation rec {
 
   doCheck = false;
 
-  # The install expects the pkgconfig directory to exist in 5.9
-  preInstall = ''
-    mkdir -p "$out/lib/pkgconfig"
-  '';
-
   # When building a wide-character (Unicode) build, create backward
   # compatibility links from the the "normal" libraries to the
   # wide-character libraries (e.g. libncurses.so to libncursesw.so).