Bazel BUILD file: grpc++_unsecure does not build (v1.0.x branch)

[mrry]

When attempting to build the latest code from the v1.0.x as part of TensorFlow, I got the following errors:

ERROR: /var/lib/jenkins/workspace/tensorflow-cl-cpu/bazel-ci_build-cache/.cache/bazel/_bazel_jenkins/eab0d61a99b6696edb3d2aff87b585e8/external/grpc/BUILD:1637:1: C++ compilation of rule '@grpc//:grpc++_unsecure' failed: gcc failed: error executing command 
  (cd /var/lib/jenkins/workspace/tensorflow-cl-cpu/bazel-ci_build-cache/.cache/bazel/_bazel_jenkins/eab0d61a99b6696edb3d2aff87b585e8/execroot/workspace && \
  exec env - \
    LD_LIBRARY_PATH='' \
    PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin \
  /usr/bin/gcc -U_FORTIFY_SOURCE '-D_FORTIFY_SOURCE=1' -fstack-protector -Wall -Wl,-z,-relro,-z,now -B/usr/bin -B/usr/bin -Wunused-but-set-parameter -Wno-free-nonheap-object -fno-omit-frame-pointer -MD -MF bazel-out/local-fastbuild/bin/external/grpc/_objs/grpc++_unsecure/external/grpc/src/core/lib/iomgr/closure.pic.d -fPIC -iquote external/grpc -iquote bazel-out/local-fastbuild/genfiles/external/grpc -iquote external/protobuf -iquote bazel-out/local-fastbuild/genfiles/external/protobuf -iquote external/bazel_tools -iquote bazel-out/local-fastbuild/genfiles/external/bazel_tools -iquote external/nanopb_git -iquote bazel-out/local-fastbuild/genfiles/external/nanopb_git -isystem external/grpc/include -isystem bazel-out/local-fastbuild/genfiles/external/grpc/include -isystem external/grpc -isystem bazel-out/local-fastbuild/genfiles/external/grpc -isystem external/protobuf/src -isystem bazel-out/local-fastbuild/genfiles/external/protobuf/src -isystem external/bazel_tools/tools/cpp/gcc3 -fno-canonical-system-headers -Wno-builtin-macro-redefined '-D__DATE__="redacted"' '-D__TIMESTAMP__="redacted"' '-D__TIME__="redacted"' -c external/grpc/src/core/lib/iomgr/closure.c -o bazel-out/local-fastbuild/bin/external/grpc/_objs/grpc++_unsecure/external/grpc/src/core/lib/iomgr/closure.pic.o): com.google.devtools.build.lib.shell.BadExitStatusException: Process exited with status 1.
external/grpc/src/core/lib/iomgr/closure.c: In function 'grpc_closure_list_fail_all':
external/grpc/src/core/lib/iomgr/closure.c:62:3: error: 'for' loop initial declarations are only allowed in C99 mode
   for (grpc_closure *c = list->head; c != NULL; c = c->next_data.next) {
   ^
external/grpc/src/core/lib/iomgr/closure.c:62:3: note: use option -std=c99 or -std=gnu99 to compile your code

For some reason a .c file is being compiled as part of building the (C++) grpc++_unsecure library. That library doesn't have a -std=gnu99 copt, so we get a failure. On further inspection (i) this code is included in grpc_unsecure, and attempting to link grpc++_unsecure into a shared object fails because it links both grpc++_unsecure.a and grpc_unsecure.a, and some symbols are defined in both.

The solution seems to be to remove all of the .c files from the grpc++_unsecure rule. We're doing that in TensorFlow with a substituted BUILD file (not yet public), but we'd love to switch the upstream one from gRPC!

(FWIW, it looks like the grpc++ rule might have the same problem.)

[ioctl0]

FWIW, grpc++ definitely doesn't build either, with the same root cause. The symptom I'm seeing is tons of duplicate symbols at link time -- most of the .c files are srcs for both the 'grpc++' target and 'grpc', which it depends on.

[xyzzyz]

I think #8055 should fix this.