lockdep: add -fcommon workaround

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

ld: lockdep.o:/build/linux-5.0.21/tools/lib/lockdep/../../include/linux/rcu.h:5: multiple definition of
`rcu_scheduler_active'; common.o:/build/linux-5.0.21/tools/lib/lockdep/../../include/linux/rcu.h:5: first defined here

+6
+6
pkgs/os-specific/linux/lockdep/default.nix
··· 23 23 24 24 nativeBuildInputs = [ flex bison ]; 25 25 26 + # Workaround build failure on -fno-common toolchains like upstream 27 + # gcc-10. Otherwise build fails as: 28 + # ld: lockdep.o:/build/linux-5.0.21/tools/lib/lockdep/../../include/linux/rcu.h:5: multiple definition of 29 + # `rcu_scheduler_active'; common.o:/build/linux-5.0.21/tools/lib/lockdep/../../include/linux/rcu.h:5: first defined here 30 + NIX_CFLAGS_COMPILE = "-fcommon"; 31 + 26 32 buildPhase = '' 27 33 make defconfig 28 34 make headers_install