Changes

[zorg] Pass "-DLLVM_POLLY_LINK_INTO_TOOLS=ON" in getPollyBuildFactory
The default here was changed recently, and the 
aosp-O3-polly-before-vectorizer-unprofitable builder assumes polly is 
linked into clang.
Differential Revision: https://reviews.llvm.org/D72646

[AVR] Add the AVR builder 'llvm-avr-linux' back, pulling from GitHub
This patch brings back the existing AVR builder that was removed in 
3b645861c5110a9d11bf5f6d936ca074212cc452 due to it being incompatible 
with the GitHub only repo we now have.
The builder now uses the 'getClangCMakeBuildFactory()' factory, instead 
of 'getLLVMCMakeBuildFactory()' as it used to.

lldb-sanitized: Move MAX_PARALLEL_TESTS initialization to a place where
it can actually affect the cmake invocation.