stdenv: add first iteration of the multiout hook

Now it should contain *all* information from stdenv/setup.sh of
the original mutiple-output branch.
However, the configurability of the output paths is much greater.

pkgs/build-support/setup-hooks/multiple-outputs.sh

@@ -0,0 +1,51 @@
+preConfigureHooks+=(_multioutConfig)
+
+# Assign the first nonempty string to variable named $1
+_assignFirst() {
+    local varName="$1"
+    shift
+    while [ $# -ge 0 ]; do
+        if [ -n "$1" ]; then eval "${varName}"="$1"; return; fi
+        shift
+    done
+    return 1 # none found
+}
+
+# Setup chains of sane default values with easy overridability.
+# The variables are global to be usable anywhere during the build.
+# ToDo: I was unable to get rid of the double-name redundancy (I hate bash eval ways)
+
+_assignFirst outputDev "$outputDev" "$dev" "$out"
+_assignFirst outputBin "$outputBin" "$bin" "$out"
+
+_assignFirst outputInclude "$outputInclude" "$outputDev"
+
+# so-libs are often among the main things to keep, and so go to $out
+_assignFirst outputLib "$outputLib" "$lib" "$out"
+
+_assignFirst outputDoc "$outputDoc" "$doc" "$out"
+# man and info pages are small and often useful to distribute with binaries
+_assignFirst outputMan "$outputMan" "$man" "$outputBin"
+_assignFirst outputInfo "$outputInfo" "$info" "$outputMan"
+
+# Add standard flags to put files into the desired outputs.
+_multioutConfig() {
+    if [ -n "${setOutputFlags-1}" ]; then
+        configureFlags="\
+            --bindir=$outputBin/bin --sbindir=$outputBin/sbin --libexecdir=$outputBin/libexec \
+            --includedir=$outputInclude/include --oldincludedir=$outputInclude/include \
+            --mandir=$outputMan/share/man --infodir=$outputInfo/share/info --docdir=$outputDoc/share/doc \
+            --libdir=$outputLib/lib \
+            $configureFlags"
+
+        installFlags="\
+            pkgconfigdir=$outputDev/lib/pkgconfig \
+            m4datadir=$outputDev/share/aclocal aclocaldir=$outputDev/share/aclocal \
+            $installFlags"
+    fi
+}
+
+# Add rpath prefixes to library paths, and avoid stdenv doing it for $out.
+_addRpathPrefix "$outputLib"
+NIX_NO_SELF_RPATH=1
+

pkgs/stdenv/generic/default.nix

@@ -206,6 +206,12 @@ let
       inherit overrides;
 
       inherit gcc;
+
+      # extra useful hooks, so we do not need to pass them as package arguments
+      hookLib = {
+        multiout = ../../build-support/setup-hooks/multiple-outputs.sh;
+        #ToDo: add also autoreconf = pkgs.autoreconfHook
+      };
     }
 
     # Propagate any extra attributes.  For instance, we use this to

pkgs/stdenv/generic/setup.sh

@@ -259,16 +259,19 @@ for i in $crossPkgs; do
 done
 
 
-# Add the output as an rpath. ToDo: multiple-output?
-if [ "$NIX_NO_SELF_RPATH" != 1 ]; then
-    export NIX_LDFLAGS="-rpath $out/lib $NIX_LDFLAGS"
+# Add $1/lib* into rpaths.
+_addRpathPrefix() {
+    if [ "$NIX_NO_SELF_RPATH" != 1 ]; then
+        export NIX_LDFLAGS="-rpath $1/lib $NIX_LDFLAGS"
         if [ -n "$NIX_LIB64_IN_SELF_RPATH" ]; then
-        export NIX_LDFLAGS="-rpath $out/lib64 $NIX_LDFLAGS"
+            export NIX_LDFLAGS="-rpath $1/lib64 $NIX_LDFLAGS"
         fi
         if [ -n "$NIX_LIB32_IN_SELF_RPATH" ]; then
-        export NIX_LDFLAGS="-rpath $out/lib32 $NIX_LDFLAGS"
+            export NIX_LDFLAGS="-rpath $1/lib32 $NIX_LDFLAGS"
         fi
-fi
+    fi
+}
+_addRpathPrefix "$out"
 
 
 # Set the TZ (timezone) environment variable, otherwise commands like