1. Fix MINIMAL build.
  (a) Add a void cast to a var only used in asserts.
  (b) Use "REQUIRES:" instead of "REQUIRES" in a .ll file.
2. Use StrError instead of StrDump for errors.
3. Use a lambda instead of a functor because C++11.
4. Explicit check for -filetype=obj in a non-dump-enabled build, to avoid cryptic downstream error messages.
5. Run "make format" which was neglected earlier.

BUG= none
R=kschimpf@google.com

Review URL: https://codereview.chromium.org/1284493003.