I set up a simple hello world cpp project so I could test the bazel crosstool tutorial to run a bazel built executable on a raspberry pi. First, I set up and built a simple project:

~/projects/bazel_examples$ tree -L 1 src/cpp   
cpp
├── BUILD
├── hello_lib.cpp
├── hello_lib.h
└── main.cpp
~/projects/bazel_examples$ bazel build //src/cpp:hello
INFO: Analysed target //src/cpp:hello (4 packages loaded).
INFO: Found 1 target...
Target //src/cpp:hello up-to-date:
  bazel-bin/src/cpp/hello
INFO: Elapsed time: 1.348s, Critical Path: 0.44s
INFO: Build completed successfully, 7 total actions
~/projects/bazel_examples$ bazel-bin/src/cpp/hello
Hello world! 0
Hello world! 1
Hello world! 2
Hello world! 3
Hello world! 4
Hello world! 5

Following the guide in the bazel wiki and modifying the bazel example project, I was able to crosscompile and run my hello world example on a raspberry pi 2.

~/projects/bazel_examples$ bazel build --crosstool_top=//tools/arm_compiler:toolchain --cpu=rpi  //src/cpp:hello
INFO: Analysed target //src/cpp:hello (0 packages loaded).
INFO: Found 1 target...
Target //src/cpp:hello up-to-date:
  bazel-bin/src/cpp/hello
INFO: Elapsed time: 7.164s, Critical Path: 6.97s
INFO: Build completed successfully, 3 total actions

Copying the file to the pi shows that it executes nominally:

pi@raspberrypi:~ $ uname -a
Linux raspberrypi 4.9.59-v7+ #1047 SMP Sun Oct 29 12:19:23 GMT 2017 armv7l GNU/Linux
pi@raspberrypi:~ $ ./hello
Hello world! 0
Hello world! 1
Hello world! 2
Hello world! 3
Hello world! 4
Hello world! 5

Code available here:

https://github.com/curtismuntz/bazel_examples

Update December 2018

I have relocated the bazel crosstool logic into its own repository, allowing for trivial inclusion to your projects. It can now be found here:

https://gitlab.com/murtis/bazel_compilers

Simply add to your WORKSPACE file:

http_archive(
    name = "murtis_bazel_compilers",
    url = "https://gitlab.com/murtis/bazel_compilers/-/archive/v0.1.0/bazel_compilers-v0.1.0.tar.gz",
    strip_prefix = 'bazel_compilers-v0.1.0',
    sha256 = "8802d0187bcee2f4f20ca885608fa99fe759962db02845f53eaaa929dc8e3c15"
)

load("@murtis_bazel_compilers//compilers:dependencies.bzl", "cross_compiler_dependencies")

cross_compiler_dependencies()

Note that the repository may have a newer version than this post references. Next, in your .bazelrc file:

build --compiler=compiler

build:armv7hf --crosstool_top=@murtis_bazel_compilers//compilers/arm_compiler:toolchain
build:armv7hf --host_crosstool_top=@bazel_tools//tools/cpp:toolchain
build:armv7hf --cpu=armeabi-v7a --compiler=gcc
build:armv7hf --spawn_strategy=standalone

You can then build with:

~/projects/bazel_examples$ bazel build --config=armv7hf  //src/cpp:hello