Release 0.26.1 (2019-06-06)

Baseline: c2001a4

Cherry picks:

   + e67c961:
     Fix a non-determinism in create_embedded_tools.py.
   + 81aefe7:
     Remove unsupported cpu attribute from cc_toolchains.
   + 597e289:
     remote: made CombinedCache a composition of Disk and Http Cache
   + 942f7cf:
     C++: Fixes bug in C++ API with external repo aspects
   + 85a5a2b:
     Configure @androidsdk//:emulator_x86 and :emulator_arm to point
     to the unified emulator binary
   + 9835cb4:
     Automated rollback of commit
     844e4e2.
   + c963ba2:
     Windows, Python: fix arg. esc. also in host config
   + a1ea487:
     Do not pre-cache changed files under managed directories
   + 7dc78cd:
     Add explicit execution and target constraints for autodiscovered
     cc t?
   + dd9ac13:
     Fix a bug when a relative path is used for the execution log
   + 0ff19c6:
     Fix StandaloneTestStrategy.appendStderr
   + 7f49531:
     Fix the autodetecting Python toolchain on Mac
   + ddce723:
     Avoid exporting PATH unnecessarily
   + 35dd05a:
     Allow Starlark rules to be able to use the `exec_compatible_with`
   + cb82ed8:
     Release 0.26.0 (2019-05-28)
   + d1c0d20:
     Allow WORKSPACE file to be a symlink if no managed directories
     is used.
   + c3d2aa7:
     Fix ios, tvos and watchos arm64 constraints
   + 55e4205:
     Bump java_tools_javac10 from 3.1 to 3.2

Patch release on top of 0.26.0, fixing
- bazelbuild#8475
- bazelbuild#8520
- bazelbuild/intellij#845