avrlibc: hook up libdir for cc-wrapper

-B must be set to the root directory of avrlibc, otherwise gcc cannot
locate crt objects for some attiny devices. -L trains as set by
bintools-wrapper are not necessary with -B set correctly because gcc
takes care of that, and likewise we can drop the -B train from
cc-wrapper because the one spec is enough.

pkgs/build-support/bintools-wrapper/default.nix

@@ -301,12 +301,6 @@ stdenv.mkDerivation {
       hardening_unsupported_flags+=" relro bindnow"
     ''
 
-    + optionalString (libc != null && targetPlatform.isAvr) ''
-      for isa in avr5 avr3 avr4 avr6 avr25 avr31 avr35 avr51 avrxmega2 avrxmega4 avrxmega5 avrxmega6 avrxmega7 tiny-stack; do
-        echo "-L${getLib libc}/avr/lib/$isa" >> $out/nix-support/libc-cflags
-      done
-    ''
-
     + optionalString stdenv.targetPlatform.isDarwin ''
       echo "-arch ${targetPlatform.darwinArch}" >> $out/nix-support/libc-ldflags
     ''

pkgs/build-support/cc-wrapper/default.nix

@@ -649,12 +649,6 @@ stdenv.mkDerivation {
       hardening_unsupported_flags+=" stackprotector"
     ''
 
-    + optionalString (libc != null && targetPlatform.isAvr) ''
-      for isa in avr5 avr3 avr4 avr6 avr25 avr31 avr35 avr51 avrxmega2 avrxmega4 avrxmega5 avrxmega6 avrxmega7 tiny-stack; do
-        echo "-B${getLib libc}/avr/lib/$isa" >> $out/nix-support/libc-crt1-cflags
-      done
-    ''
-
     + optionalString stdenv.targetPlatform.isDarwin ''
         echo "-arch ${targetPlatform.darwinArch}" >> $out/nix-support/cc-cflags
     ''

pkgs/development/misc/avr/libc/default.nix

@@ -19,6 +19,7 @@ stdenv.mkDerivation rec {
 
   passthru = {
     incdir = "/avr/include";
+    libdir = "/avr/lib";
   };
 
   meta = with lib; {