treewide: configureFlags is a flat list

pkgs/development/compilers/gcc/common/configure-flags.nix

@@ -153,7 +153,7 @@ let
     ++ lib.optional (langJava && javaAntlr != null) "--with-antlr-jar=${javaAntlr}"
 
     ++ (import ../common/platform-flags.nix { inherit (stdenv) lib targetPlatform; })
-    ++ lib.optional (targetPlatform != hostPlatform) crossConfigureFlags
+    ++ lib.optionals (targetPlatform != hostPlatform) crossConfigureFlags
     ++ lib.optional (targetPlatform != hostPlatform) "--disable-bootstrap"
 
     # Platform-specific flags

pkgs/development/libraries/qt-5/modules/qtbase.nix

@@ -170,11 +170,6 @@ stdenv.mkDerivation {
     export LD=$CXX
     ''}
 
-    configureFlags+="\
-        -plugindir $out/$qtPluginPrefix \
-        -qmldir $out/$qtQmlPrefix \
-        -docdir $out/$qtDocPrefix"
-
     NIX_CFLAGS_COMPILE+=" -DNIXPKGS_QT_PLUGIN_PREFIX=\"$qtPluginPrefix\""
   '';
 
@@ -222,6 +217,10 @@ stdenv.mkDerivation {
   # TODO Remove obsolete and useless flags once the build will be totally mastered
   configureFlags =
     [
+      "-plugindir $(out)/$(qtPluginPrefix)"
+      "-qmldir $(out)/$(qtQmlPrefix)"
+      "-docdir $(out)/$(qtDocPrefix)"
+
       "-verbose"
       "-confirm-license"
       "-opensource"

pkgs/misc/ghostscript/default.nix

@@ -76,15 +76,19 @@ stdenv.mkDerivation rec {
     sed "s@^ZLIBDIR=.*@ZLIBDIR=${zlib.dev}/include@" -i configure.ac
 
     autoconf
-  '' + lib.optionalString cupsSupport ''
-    configureFlags="$configureFlags --with-cups-serverbin=$out/lib/cups --with-cups-serverroot=$out/etc/cups --with-cups-datadir=$out/share/cups"
   '';
 
-  configureFlags =
-    [ "--with-system-libtiff"
-      "--enable-dynamic"
-    ] ++ lib.optional x11Support "--with-x"
-      ++ lib.optional cupsSupport "--enable-cups";
+  configureFlags = [
+    "--with-system-libtiff"
+    "--enable-dynamic"
+  ]
+  ++ lib.optional x11Support "--with-x"
+  ++ lib.optionals cupsSupport [
+    "--enable-cups"
+    "--with-cups-serverbin=$(out)/lib/cups"
+    "--with-cups-serverroot=$(out)/etc/cups"
+    "--with-cups-datadir=$(out)/share/cups"
+  ];
 
   doCheck = true;
 

pkgs/tools/networking/dhcp/default.nix

@@ -36,8 +36,8 @@ stdenv.mkDerivation rec {
     "--enable-early-chroot"
     "--sysconfdir=/etc"
     "--localstatedir=/var"
-    (lib.optional stdenv.isLinux "--with-randomdev=/dev/random")
-  ] ++ stdenv.lib.optionals (openldap != null) [ "--with-ldap" "--with-ldapcrypto" ];
+  ] ++ lib.optional stdenv.isLinux "--with-randomdev=/dev/random"
+    ++ stdenv.lib.optionals (openldap != null) [ "--with-ldap" "--with-ldapcrypto" ];
 
   NIX_CFLAGS_COMPILE = builtins.toString [
     "-Wno-error=pointer-compare"

pkgs/tools/networking/vde2/default.nix

@@ -15,7 +15,7 @@ stdenv.mkDerivation rec {
     }
   );
 
-  configureFlags = stdenv.lib.optional (!withPython) [ "--disable-python" ];
+  configureFlags = stdenv.lib.optional (!withPython) "--disable-python";
 
   buildInputs = [ openssl libpcap ]
     ++ stdenv.lib.optional withPython python2;