~/github/ericgribkoff/grpc$ bazel build //tools/grpcz:grpcz_client --verbose_failures
INFO: Found 1 target...
ERROR: /usr/local/google/home/ericgribkoff/github/ericgribkoff/grpc/tools/grpcz/BUILD:65:1: Linking of rule '//tools/grpcz:grpcz_client' failed: gcc failed: error executing command
  (exec env - \
  /usr/bin/gcc -o bazel-out/local-fastbuild/bin/tools/grpcz/grpcz_client -pthread '-fuse-ld=gold' -Wl,-no-as-needed -Wl,-z,relro,-z,now -B/usr/bin -B/usr/bin '-Wl,--build-id=md5' '-Wl,--hash-style=gnu' -pass-exit-codes -Wl,-S -Wl,@bazel-out/local-fastbuild/bin/tools/grpcz/grpcz_client-2.params)

Use --sandbox_debug to see verbose messages from the sandbox.
/usr/bin/ld.gold: error: bazel-out/local-fastbuild/bin/external/mongoose_repo/_objs/mongoose_lib/external/mongoose_repo/mongoose.pic.o: multiple definition of 'MD5_Init'
/usr/bin/ld.gold: bazel-out/local-fastbuild/bin/external/submodule_boringssl/_objs/crypto/external/submodule_boringssl/src/crypto/md5/md5.pic.o: previous definition here
/usr/bin/ld.gold: error: bazel-out/local-fastbuild/bin/external/mongoose_repo/_objs/mongoose_lib/external/mongoose_repo/mongoose.pic.o: multiple definition of 'MD5_Update'
/usr/bin/ld.gold: bazel-out/local-fastbuild/bin/external/submodule_boringssl/_objs/crypto/external/submodule_boringssl/src/crypto/md5/md5.pic.o: previous definition here
/usr/bin/ld.gold: error: bazel-out/local-fastbuild/bin/external/mongoose_repo/_objs/mongoose_lib/external/mongoose_repo/mongoose.pic.o: multiple definition of 'MD5_Final'
/usr/bin/ld.gold: bazel-out/local-fastbuild/bin/external/submodule_boringssl/_objs/crypto/external/submodule_boringssl/src/crypto/md5/md5.pic.o: previous definition here
collect2: error: ld returned 1 exit status
Use --strategy=CppLink=standalone to disable sandboxing for the failing actions.
Target //tools/grpcz:grpcz_client failed to build
INFO: Elapsed time: 0.506s, Critical Path: 0.32s