Use a very large id bound when fuzzing the optimizer, and check that the
input does not ids that are too close to this bound. This should make it
impossible in practice for an id overflow to occur.
Fixes#4657.
Instead calculate a hash based on the input and use that as a seed
into random data generation for the target env.
Also fixes issue where input data was not actually being fed into
one fuzzer.
Fixes#4450
1.
BUILD.gn: Don't use the extra Chromium clang warnings
Also removes the unused .gn secondary_sources.
2.
Move fuzzers in test/ instead of testing/
This frees up testing/ to be the git subtree of Chromium's src/testing/
that contains test.gni, gtest, gmock and libfuzzer
3.
DEPS: get the whole testing/ subtree of Chromium
4.
BUILD.gn: Simplify the standalone gtest targets
These targets definitions are inspired from ANGLE's and add a variable
that is the path of the googletest directory so that it can be made
overridable in future commits.
6.
BUILD.gn: Add overridable variables for deps dirs
This avoids hardcoded paths to dependencies that make it hard to
integrate SPIRV-Tools in other GN projects.
