Surpress warnings in minzip/Zip.c

  bootable/recovery/minzip/Zip.c:514:5: warning: Value stored to 'compRemaining' is never read
    compRemaining = pEntry->compLen;
        ^               ~~~~~~~~~~~~~~~
  bootable/recovery/minzip/Zip.c:778:9: warning: Null pointer argument in call to memory copy function
    memcpy(p, helper->targetDir, helper->targetDirLen);
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Bug: 27229894
Change-Id: I0482bac3a4fcddc191783d1e5b5a83cf29fa4e85