shallot: add -fcommon workaround

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

ld: src/shallot.o:(.bss+0x8): multiple definition of `lucky_thread'; src/error.o:(.bss+0x8): first defined here

+5
+5
pkgs/tools/misc/shallot/default.nix
··· 30 }) 31 ]; 32 33 installPhase = '' 34 mkdir -p $out/bin 35 cp ./shallot $out/bin/
··· 30 }) 31 ]; 32 33 + # Workaround build failure on -fno-common toolchains like upstream 34 + # gcc-10. Otherwise build fails as: 35 + # ld: src/shallot.o:(.bss+0x8): multiple definition of `lucky_thread'; src/error.o:(.bss+0x8): first defined here 36 + NIX_CFLAGS_COMPILE = "-fcommon"; 37 + 38 installPhase = '' 39 mkdir -p $out/bin 40 cp ./shallot $out/bin/