The log you attached contains 6 failed build attempts.
The first one failed with these errors:
:info:build cp: /opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_llvm-3.7/clang-3.7/work/build/tools/clang/runtime/compiler-rt/clang_darwin/eprintf/libcompiler_rt.a: No such file or directory
:info:build make[3]: *** [/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_llvm-3.7/clang-3.7/work/build/Release+Debug/lib/clang/3.7.1/lib/darwin/libclang_rt.eprintf.a] Error 1
:info:build make[3]: *** Waiting for unfinished jobs....
:info:build cp: /opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_llvm-3.7/clang-3.7/work/build/tools/clang/runtime/compiler-rt/clang_darwin/10.4/libcompiler_rt.a: No such file or directory
Build attemps 2 through 6 failed with this error:
:info:build /usr/include/sys/cdefs.h:540:4: error: Unknown architecture
However those build attempt were not clean; they were resuming from the original failed build. As such, I would not pay any attention to the possibly erroneous errors they generated and I would focus on the error generated by the original build attempt.
