liburing: Fix references between outputs issue

Experienced in:
https://github.com/NixOS/nixpkgs/pull/98869#discussion_r495492213

Set configure flags properly, don't override configurePhase, per:
https://github.com/jtojnar/nixpkgs-hammering/blob/master/explanations/explicit-phases.md

Use different output names - use $bin for examples, and $out for
libraries which expectedly should be referenced by reverse deps.

pkgs/development/libraries/liburing/default.nix

@@ -14,24 +14,32 @@ stdenv.mkDerivation rec {
 
   separateDebugInfo = true;
   enableParallelBuilding = true;
-
+  # Upstream's configure script is not autoconf generated, but a hand written one.
-  outputs = [ "out" "lib" "dev" "man" ];
+  setOutputFlags = false;
-
+  preConfigure =
-  configurePhase = ''
+    # We cannot use configureFlags or configureFlagsArray directly, since we
-    ./configure \
+    # don't have structuredAttrs yet and using placeholder causes permissions
-      --prefix=$out \
+    # denied errors. Using $dev / $man in configureFlags causes bash evaluation
-      --includedir=$dev/include \
+    # errors
-      --libdir=$lib/lib \
+  ''
-      --mandir=$man/share/man \
+    configureFlagsArray+=(
+      "--includedir=$dev/include"
+      "--mandir=$man/share/man"
+    )
   '';
 
-  # Copy the examples into $out.
+  outputs = [ "out" "bin" "dev" "man" ];
-  postInstall = ''
+
-    mkdir -p $out/bin
+  postInstall =
-    cp ./examples/io_uring-cp examples/io_uring-test $out/bin
+  # Copy the examples into $bin. Most reverse dependency of this package should
-    cp ./examples/link-cp $out/bin/io_uring-link-cp
+  # reference only the $out output
-    cp ./examples/ucontext-cp $out/bin/io_uring-ucontext-cp
+  ''
-  '';
+    mkdir -p $bin/bin
+    cp ./examples/io_uring-cp examples/io_uring-test $bin/bin
+    cp ./examples/link-cp $bin/bin/io_uring-link-cp
+    cp ./examples/ucontext-cp $bin/bin/io_uring-ucontext-cp
+  ''
+  ;
 
   meta = with stdenv.lib; {
     description = "Userspace library for the Linux io_uring API";