xbursttools: add -fcommon workaround

Workaround build failure on -fno-common toolchains like upstream
gcc-10. Otherwise build fails as:

    mipsel-unknown-linux-uclibc-ld: boothandler.o:(.bss+0x8): multiple definition of
      `start_addr'; main.o:(.bss+0x8): first defined here

pkgs/tools/misc/xburst-tools/default.nix

@@ -19,6 +19,11 @@ stdenv.mkDerivation {
     sh autogen.sh
   '';
 
+  # Workaround build failure on -fno-common toolchains:
+  #   mipsel-unknown-linux-uclibc-ld: boothandler.o:(.bss+0x8): multiple definition of
+  #     `start_addr'; main.o:(.bss+0x8): first defined here
+  NIX_CFLAGS_COMPILE_FOR_TARGET = "-fcommon";
+
   configureFlags = lib.optionals (gccCross != null) [
     "--enable-firmware"
     "CROSS_COMPILE=${gccCross.targetPrefix}"