speech-tools: add -fcommon workaround

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

    ld: libestools.a(editline.o):(.bss+0x28): multiple definition of
      `editline_history_file'; libestools.a(siodeditline.o):(.data.rel.local+0x8): first defined here

pkgs/development/libraries/speech-tools/default.nix

@@ -11,6 +11,11 @@ stdenv.mkDerivation rec {
 
   buildInputs = [ alsa-lib ncurses ];
 
+  # Workaround build failure on -fno-common toolchains:
+  #   ld: libestools.a(editline.o):(.bss+0x28): multiple definition of
+  #     `editline_history_file'; libestools.a(siodeditline.o):(.data.rel.local+0x8): first defined here
+  NIX_CFLAGS_COMPILE = "-fcommon";
+
   preConfigure = ''
     sed -e s@/usr/bin/@@g -i $( grep -rl '/usr/bin/' . )
     sed -re 's@/bin/(rm|printf|uname)@\1@g' -i $( grep -rl '/bin/' . )