systems: support cross-compiling for Renesas RX microcontrollers (#173858)

lib/systems/doubles.nix

···
     # none
     "aarch64_be-none" "aarch64-none" "arm-none" "armv6l-none" "avr-none" "i686-none"
     "msp430-none" "or1k-none" "m68k-none" "powerpc-none" "powerpcle-none"
-    "riscv32-none" "riscv64-none" "s390-none" "s390x-none" "vc4-none"
+    "riscv32-none" "riscv64-none" "rx-none" "s390-none" "s390x-none" "vc4-none"
     "x86_64-none"
 
     # OpenBSD
···
   riscv         = filterDoubles predicates.isRiscV;
   riscv32       = filterDoubles predicates.isRiscV32;
   riscv64       = filterDoubles predicates.isRiscV64;
+  rx            = filterDoubles predicates.isRx;
   vc4           = filterDoubles predicates.isVc4;
   or1k          = filterDoubles predicates.isOr1k;
   m68k          = filterDoubles predicates.isM68k;

lib/systems/examples.nix

···
     libc = "newlib";
   };
 
+  rx-embedded = {
+    config = "rx-none-elf";
+    libc = "newlib";
+  };
+
   msp430 = {
     config = "msp430-elf";
     libc = "newlib";

lib/systems/inspect.nix

···
     isRiscV        = { cpu = { family = "riscv"; }; };
     isRiscV32      = { cpu = { family = "riscv"; bits = 32; }; };
     isRiscV64      = { cpu = { family = "riscv"; bits = 64; }; };
+    isRx           = { cpu = { family = "rx"; }; };
     isSparc        = { cpu = { family = "sparc"; }; };
     isWasm         = { cpu = { family = "wasm"; }; };
     isMsp430       = { cpu = { family = "msp430"; }; };

lib/systems/parse.nix

···
 
     alpha    = { bits = 64; significantByte = littleEndian; family = "alpha"; };
 
+    rx       = { bits = 32; significantByte = littleEndian; family = "rx"; };
     msp430   = { bits = 16; significantByte = littleEndian; family = "msp430"; };
     avr      = { bits = 8; family = "avr"; };
 

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

···
       else if targetPlatform.isM68k then "m68k"
       else if targetPlatform.isS390 then "s390"
       else if targetPlatform.isRiscV then "lriscv"
+      else if targetPlatform.isRx then "rx"
       else throw "unknown emulation for platform: ${targetPlatform.config}";
     in if targetPlatform.useLLVM or false then ""
        else targetPlatform.bfdEmulation or (fmt + sep + arch);

pkgs/top-level/release-cross.nix

···
   x86_64-embedded = mapTestOnCross lib.systems.examples.x86_64-embedded embedded;
   riscv64-embedded = mapTestOnCross lib.systems.examples.riscv64-embedded embedded;
   riscv32-embedded = mapTestOnCross lib.systems.examples.riscv32-embedded embedded;
+  rx-embedded = mapTestOnCross lib.systems.examples.rx-embedded embedded;
 
   x86_64-netbsd = mapTestOnCross lib.systems.examples.x86_64-netbsd common;