Fixes KhronosGroup#3529

* Make BasicBlock::reachable() only consider static reachability
* Fix reachability calculation to be independent of block order
* add tests

Roll third_party/glslang/ b481744..9eef54b (4 commits)

KhronosGroup/glslang@b481744...9eef54b

$ git log b481744..9eef54b --date=short --no-merges --format='%ad %ae %s'
2020-07-17 bclayton Update license-checker.cfg with simplified rules
2020-07-17 bclayton Add new rules for update of license-checker
2020-07-15 cepheus GLSL/SPV: Propagaet precision qualifier from function to return value.
2020-07-14 bclayton runtests: Check error codes, set LD_LIBRARY_PATH

Created with:
  roll-dep third_party/glslang

Roll third_party/googletest/ 70b90929b..a781fe29b (3 commits)

google/googletest@70b9092...a781fe2

$ git log 70b90929b..a781fe29b --date=short --no-merges --format='%ad %ae %s'
2020-07-13 ofats Googletest export
2020-07-11 ashikpaul17 Fixed some minor typos
2020-06-19 amatanhead Make EXPECT_THROW and EXPECT_NO_THROW macros more informative

Created with:
  roll-dep third_party/googletest

Roll third_party/re2/ fe8a81adc..ca11026a0 (1 commit)

google/re2@fe8a81a...ca11026

$ git log fe8a81adc..ca11026a0 --date=short --no-merges --format='%ad %ae %s'
2020-07-14 junyer Make Regexp::Simplify() return a null pointer when stopped early.

Created with:
  roll-dep third_party/re2

Roll third_party/spirv-headers/ 308bd07..7f2ae11 (1 commit)

KhronosGroup/SPIRV-Headers@308bd07...7f2ae11

$ git log 308bd07..7f2ae11 --date=short --no-merges --format='%ad %ae %s'
2020-07-19 vkushwaha Add changes for SPV_EXT_shader_atomic_float

Created with:
  roll-dep third_party/spirv-headers

Roll third_party/spirv-tools/ c9b254d..c10d6ce (19 commits)

KhronosGroup/SPIRV-Tools@c9b254d...c10d6ce

$ git log c9b254d..c10d6ce --date=short --no-merges --format='%ad %ae %s'
2020-07-20 stefanomil spirv-fuzz: refactor to use RemoveAtRandomIndex (KhronosGroup#3560)
2020-07-20 antonikarp spirv-fuzz: add TransformationAddRelaxedDecoration (KhronosGroup#3545)
2020-07-17 alanbaker Store location values sparsely (KhronosGroup#3488)
2020-07-17 dneto Permit Simple and GLSL450 memory model in WEBGPU_0 (KhronosGroup#3463)
2020-07-17 antonikarp spirv-fuzz: support floating-point in TransformationInvertComparisonOperator (KhronosGroup#3551)
2020-07-17 stefanomil Change MaybeApplyTransformation to return a boolean (KhronosGroup#3555)
2020-07-17 stefanomil spirv-fuzz: Implement MaybeApplyTransformation helper function (KhronosGroup#3540)
2020-07-17 stefanomil spirv-fuzz: Assert false in IsApplicable method of TransformationAccessChain (KhronosGroup#3528)
2020-07-16 vasniktel spirv-fuzz: Add support for OpBitcast to TransformationEquationInstruction (KhronosGroup#3523)
2020-07-16 vasniktel spirv-fuzz: Add support for OpConvert to TransformationEquationInstruction (KhronosGroup#3472)
2020-07-15 alanbaker Fix reachability in the validator (KhronosGroup#3541)
2020-07-15 vasniktel spirv-fuzz: Remove TransformationCopyObject (KhronosGroup#3531)
2020-07-15 vasniktel spirv-opt: Add support for OpLabel to dominator analysis (KhronosGroup#3516)
2020-07-15 stefanomil spirv-fuzz: Fuzzer pass to interchange zero-like constants (KhronosGroup#3524)
2020-07-15 afdx spirv-fuzz: Add replay range option (KhronosGroup#3535)
2020-07-14 jaebaek Rewrite KillDebugDeclares() (KhronosGroup#3513)
2020-07-14 andreperezmaselco.developer spirv-fuzz: Fix instruction insertion issue (KhronosGroup#3521)
2020-07-14 andreperezmaselco.developer spirv-fuzz: Implement the OpMatrixTimesMatrix linear algebra case (KhronosGroup#3527)
2020-07-14 greg Add support to GPU-AV instrumentation for Task and Mesh shaders (KhronosGroup#3512)

Created with:
  roll-dep third_party/spirv-tools