Since the remote Shell test execution feature was added, these tests
should now be disabled on Windows target instead of Windows host.
It should fix failures on
https://lab.llvm.org/staging/#/builders/197/builds/76.
"line 0" in a DWARF linetable means something that doesn't have associated
source. The code for mixed disassembly has a comment indicating that
"line 0" should be skipped, but the wrong value was returned. Fix the return
value and add a test to check that we don't incorrectly show source lines
from the beginning of the file.
Reviewed By: jasonmolenda
Differential Revision: https://reviews.llvm.org/D112931
