qtbase: don't patch non-existent .pc files on Darwin

pkgs/development/libraries/qt-5/5.6/qtbase/default.nix

@@ -267,10 +267,20 @@ stdenv.mkDerivation {
               done
           popd
       fi
+    ''
 
-      # fixup .pc file (where to find 'moc' etc.)
+    # fixup .pc file (where to find 'moc' etc.)
-      sed "s|^host_bins=.*|host_bins=$dev/bin|" -i "$dev/lib/pkgconfig/Qt5Core.pc"
+    + lib.optionalString (!stdenv.isDarwin) ''
-    '' + lib.optionalString stdenv.isDarwin ''
+      sed -i "$dev/lib/pkgconfig/Qt5Core.pc" \
+          "s|^host_bins=.*|host_bins=$dev/bin|"
+    ''
+
+    # Don't move .prl files on darwin because they end up in
+    # "dev/lib/Foo.framework/Foo.prl" which interferes with subsequent
+    # use of lndir in the qtbase setup-hook. On Linux, the .prl files
+    # are in lib, and so do not cause a subsequent recreation of deep
+    # framework directory trees.
+    + lib.optionalString stdenv.isDarwin ''
       fixDarwinDylibNames_rpath() {
         local flags=()
 

pkgs/development/libraries/qt-5/5.7/qtbase/default.nix

@@ -228,10 +228,14 @@ stdenv.mkDerivation {
               done
           popd
       fi
-
-      # fixup .pc file (where to find 'moc' etc.)
-      sed "s|^host_bins=.*|host_bins=$dev/bin|" -i "$dev/lib/pkgconfig/Qt5Core.pc"
     ''
+
+    # fixup .pc file (where to find 'moc' etc.)
+    + lib.optionalString (!stdenv.isDarwin) ''
+      sed -i "$dev/lib/pkgconfig/Qt5Core.pc" \
+          "s|^host_bins=.*|host_bins=$dev/bin|"
+    ''
+
     # Don't move .prl files on darwin because they end up in
     # "dev/lib/Foo.framework/Foo.prl" which interferes with subsequent
     # use of lndir in the qtbase setup-hook. On Linux, the .prl files

pkgs/development/libraries/qt-5/5.8/qtbase/default.nix

@@ -225,10 +225,14 @@ stdenv.mkDerivation {
               done
           popd
       fi
-
-      # fixup .pc file (where to find 'moc' etc.)
-      sed "s|^host_bins=.*|host_bins=$dev/bin|" -i "$dev/lib/pkgconfig/Qt5Core.pc"
     ''
+
+    # fixup .pc file (where to find 'moc' etc.)
+    + lib.optionalString (!stdenv.isDarwin) ''
+      sed -i "$dev/lib/pkgconfig/Qt5Core.pc" \
+          "s|^host_bins=.*|host_bins=$dev/bin|"
+    ''
+
     # Don't move .prl files on darwin because they end up in
     # "dev/lib/Foo.framework/Foo.prl" which interferes with subsequent
     # use of lndir in the qtbase setup-hook. On Linux, the .prl files