ART: Extend ISA features option for (host) run tests

ART: Extend ISA features option for (host) run tests

To allow to test advanced intrinsics only available on (fairly)
modern processors, and because our build requirements are still
too low to enable them in the build system, pipe through the
existing make variables to the run-tests to allow to override
the dex2oat autodetection scheme.

Usage (standalone run-test): use the new --instruction-set-features
command line parameter to set the value for dex2oat (in the prebuild
configuration) or as an -Xcompiler-option (for no-prebuild). Note:
this is general and also works for target tests.

Usage (through make): set DEX2OAT_HOST_INSTRUCTION_SET_FEATURES and
2ND_DEX2OAT_HOST_INSTRUCTION_SET_FEATURES to set instruction set
features, as was possible before for the compilation of core files.
This option is now forwarded to host run-tests.

Change-Id: I9d89c82b6a5c8853748e5d1c153dde5d4050757a