Move disabled warnings to test_compiler.py

Bug: http://b/62292583

Hard-code the disabled warnings in test_compiler.py instead of the
wrapper, and pass it to the wrapper through an environment variable.
These warnings are disabled only for the continuous build with the next
Clang version.

Test: Build the aosp-master-plus-llvm branch
Change-Id: I8fed75dc3d078b4bf0914dcdf2b4ec41214835c8