Sandbox emp_ematch genrules

These genrules already work with sandboxing, but bison emits #line
directives that reference filepaths. These paths differ between
sandboxed and non-sandboxed builds, which caused
genrule_sandboxing_test.py to think that they didn't work with
sandboxing.

Bug: 307824623
Test: ./build/soong/tests/genrule_sandbox_test.py emp_ematch.yacc.c emp_ematch.yacc.h
Change-Id: I85ed0f80dee7997af6b08a37b12e9c0ad0bd8386