This seems a recent regression, but a git blame/log on relocs.c or relocs_64.c didn't tell me anything about the source. 

HOSTCC  scripts/mod/mk_elfconfig
  CC      scripts/mod/empty.o
  CC      scripts/mod/devicetable-offsets.s
  HOSTCC  scripts/selinux/mdp/mdp
  HOSTCC  scripts/selinux/genheaders/genheaders
In file included from /mnt/host/source/src/third_party/kernel/v4.4/arch/x86/tools/relocs_64.c:17:
/mnt/host/source/src/third_party/kernel/v4.4/arch/x86/tools/relocs.c:980:6: warning: variable 'do_reloc' is used uninitialized whenever 'if'
      condition is false [-Wsometimes-uninitialized]
        if (!use_real_mode)
            ^~~~~~~~~~~~~~
/mnt/host/source/src/third_party/kernel/v4.4/arch/x86/tools/relocs.c:992:14: note: uninitialized use occurs here
        walk_relocs(do_reloc);
                    ^~~~~~~~
/mnt/host/source/src/third_party/kernel/v4.4/arch/x86/tools/relocs.c:980:2: note: remove the 'if' if its condition is always true
        if (!use_real_mode)
        ^~~~~~~~~~~~~~~~~~~
/mnt/host/source/src/third_party/kernel/v4.4/arch/x86/tools/relocs.c:977:24: note: initialize the variable 'do_reloc' to silence this
      warning
                        const char *symname);
                                            ^