bazel: add uber's hermetic c++ toolchain

[AlexTereshenkov]

Using https://github.com/uber/hermetic_cc_toolchain to build c++ code hermetically without having access to a local c++ toolchain.

Run

$ bazel build --toolchain_resolution_debug=".*" --config=hermetic-linux-amd64 //...

to see the toolchain resolution process and to build all targets for linux-amd64, hermetically.

Using a particular glibc:

$ ldd --version
ldd (Ubuntu GLIBC 2.31-0ubuntu9.17) 2.31

---

Building all targets (including test targets) works fine and one can even run the test binaries:

$ bazel-bin/test/geometry/rectangle-gtest-test                                     
Running main() from gmock_main.cc
[==========] Running 2 tests from 1 test suite.
[----------] Global test environment set-up.
[----------] 2 tests from RectangleTest
[ RUN      ] RectangleTest.GetRectangleArea
[       OK ] RectangleTest.GetRectangleArea (0 ms)
[ RUN      ] RectangleTest.GetRectangleAreaIfIsASquare
[       OK ] RectangleTest.GetRectangleAreaIfIsASquare (0 ms)
[----------] 2 tests from RectangleTest (0 ms total)

[----------] Global test environment tear-down
[==========] 2 tests from 1 test suite ran. (0 ms total)
[  PASSED  ] 2 tests.

however, the test command fails when run via the bazel test:

$ bazel test --toolchain_resolution_debug=".*" --config=hermetic-linux-amd64 //...
==================== Test output for //test/geometry:rectangle-gtest-test:
/home/user/.cache/bazel/_bazel_homeuser/51966dc905d3201ed8d44fb4278efba7/sandbox/linux-sandbox/1252/execroot/_main/bazel-out/k8-fastbuild/bin/test/geometry/rectangle-gtest-test.runfiles/_main/test/geometry/rectangle-gtest-test: error while loading shared libraries: bazel-out/k8-fastbuild/bin/_solib_k8/libsrc_Sgeometry_Slibrectangle.so: cannot open shared object file: No such file or directory

This is resolved by linking the test targets statically, see https://bazel.build/reference/be/c-cpp#cc_test

[AlexTereshenkov]

This is required otherwise getting error: unable to create compilation: ReadOnlyFileSystem.

[AlexTereshenkov]

Submitted a patch in uber/hermetic_cc_toolchain#221