genodeSources: make shared library references absolute

Use patchelf in a postFixupHook to replace any relative library names
with absolute file-sytsem paths. This ensures that the proper runtime
closures are constructed and makes it easier to route the loader to the
correct ROMs.

This requires that packages built from the Genode depot must specify
runtime dependencies as "buildInputs" in the depot-targets.nix file.

packages/genodelabs/default.nix

@@ -125,10 +125,46 @@ let
 
   stdenv' = pkgs.stdenvAdapters.overrideCC pkgs.stdenv toolchain;
 
+  patchRelativeLibraries = ''
+    if [ -z "''${noAbsoluteLibraries:-}" ]; then
+        find "''${!outputBin}" "''${!outputLib}" -type f | while read -r elf; do
+            if ! isELF "$elf"; then continue; fi
+            args=
+            for name in $(patchelf --print-needed "$elf"); do
+                if [ "ld.lib.so" == "$name" ]; then
+                    continue
+                fi
+                if [ -f "$name" ]; then
+                    continue
+                fi
+                argPair=
+                for input in ''${!outputLib} ''${libraryBuildInputs:-}; do
+                    local libdir="$input/lib"
+                    local libabs=$(realpath "$libdir/$name" 2>/dev/null || true)
+                    if [ -f "$libabs" ]; then
+                        echo "Replace $name reference with $libabs"
+                        argPair="--replace-needed $name $libabs"
+                        break
+                    fi
+                done
+                if [ -z "$argPair" ]; then
+                    echo "Could not find absolute path to $name in buildInputs"
+                    exit 1
+                fi
+                args="$args $argPair"
+            done
+            if [ -n "$args" ]; then
+                patchelf $args $elf
+            fi
+        done
+    fi
+  '';
+
   buildUpstream =
     # Build from the Genode sources
-    { name, targets, portInputs ? [ ], nativeBuildInputs ? [ ], patches ? [ ]
-    , enableParallelBuilding ? true, meta ? { }, ... }@extraAttrs:
+    { name, targets, portInputs ? [ ], nativeBuildInputs ? [ ]
+    , buildInputs ? [ ], patches ? [ ], enableParallelBuilding ? true
+    , meta ? { }, ... }@extraAttrs:
     let havePatches = patches != [ ];
 
     in stdenv'.mkDerivation (extraAttrs // {
@@ -172,6 +208,9 @@ let
         runHook postInstall
       '';
 
+      libraryBuildInputs = map pkgs.stdenv.lib.getLib buildInputs;
+      postFixup = patchRelativeLibraries;
+
       meta = { platforms = lib.platforms.genode; } // meta;
     });
 
@@ -230,6 +269,9 @@ let
         runHook postInstall
       '';
 
+      libraryBuildInputs = map pkgs.stdenv.lib.getLib buildInputs;
+      postFixup = patchRelativeLibraries;
+
       meta = { platforms = lib.platforms.genode; } // meta;
     });