U-Boot: Add AArch64 QEMU build

See

https://github.com/u-boot/u-boot/blob/master/doc/README.qemu-arm

on how to use it.

pkgs/misc/uboot/default.nix

@@ -158,6 +158,12 @@ in rec {
     filesToInstall = ["u-boot-sunxi-with-spl.bin"];
   };
 
+  ubootQemuAarch64 = buildUBoot rec {
+    defconfig = "qemu_arm64_defconfig";
+    extraMeta.platforms = ["aarch64-linux"];
+    filesToInstall = ["u-boot.bin"];
+  };
+
   ubootQemuArm = buildUBoot rec {
     defconfig = "qemu_arm_defconfig";
     extraMeta.platforms = ["armv7l-linux"];

pkgs/top-level/all-packages.nix

@@ -13872,6 +13872,7 @@ with pkgs;
     ubootOdroidXU3
     ubootOrangePiPc
     ubootPcduino3Nano
+    ubootQemuAarch64
     ubootQemuArm
     ubootRaspberryPi
     ubootRaspberryPi2