treewide: use gnu toolchain for avr/arm-embedded

These packages should in theory work with our GCC toolchains, but
there are some definite breakages that need to be tracked down.
Comparing output of these to old gcc-arm-embedded is important.

Affected packages include:

- axolooti
- avrdudess
- opentx
- microscheme
- betaflight
- inav
- blackmagic
- simavr
- gnuk

pkgs/development/misc/newlib/default.nix

@@ -23,12 +23,13 @@ in stdenv.mkDerivation {
     "--disable-nls"
     "--enable-newlib-io-long-long"
     "--enable-newlib-register-fini"
+    "--enable-newlib-retargetable-locking"
   ];
 
   dontDisableStatic = true;
 
   passthru = {
-    incdir = "/${stdenv.hostPlatform.config}/include";
-    libdir = "/${stdenv.hostPlatform.config}/lib";
+    incdir = "/${stdenv.targetPlatform.config}/include";
+    libdir = "/${stdenv.targetPlatform.config}/lib";
   };
 }

pkgs/development/misc/stm32/betaflight/default.nix

@@ -1,5 +1,5 @@
 { stdenv, fetchFromGitHub
-, gcc-arm-embedded, python2
+, gcc-arm-embedded, binutils-arm-embedded, python2
 , skipTargets ? [
   # These targets do not build, for the reasons listed, along with the last version checked.
   # Probably all of the issues with these targets need to be addressed upstream.
@@ -24,8 +24,8 @@ in stdenv.mkDerivation rec {
     sha256 = "1wyp23p876xbfi9z6gm4xn1nwss3myvrjjjq9pd3s0vf5gkclkg5";
   };
 
-  buildInputs = [
-    gcc-arm-embedded
+  nativeBuildInputs = [
+    gcc-arm-embedded binutils-arm-embedded
     python2
   ];
 
@@ -58,7 +58,6 @@ in stdenv.mkDerivation rec {
     homepage = https://github.com/betaflight/betaflight;
     license = licenses.gpl3;
     maintainers = with maintainers; [ elitak ];
-    platforms = [ "i686-linux" "x86_64-linux" ];
   };
 
 }

pkgs/development/misc/stm32/inav/default.nix

@@ -1,5 +1,5 @@
 { stdenv, fetchFromGitHub
-, gcc-arm-embedded, ruby
+, gcc-arm-embedded, binutils-arm-embedded, ruby
 }:
 
 let
@@ -17,8 +17,8 @@ in stdenv.mkDerivation rec {
     sha256 = "15zai8qf43b06fmws1sbkmdgip51zp7gkfj7pp9b6gi8giarzq3y";
   };
 
-  buildInputs = [
-    gcc-arm-embedded
+  nativeBuildInputs = [
+    gcc-arm-embedded binutils-arm-embedded
     ruby
   ];
 
@@ -50,7 +50,6 @@ in stdenv.mkDerivation rec {
     homepage = https://inavflight.github.io;
     license = licenses.gpl3;
     maintainers = with maintainers; [ elitak ];
-    platforms = [ "i686-linux" "x86_64-linux" ];
   };
 
 }