We failed to correctly parse files that executed from the very start of
the file due to a missing '- line XXX'. We now use the 'Ir' indicator to
recognize the beginning of a file.

Change-Id: I529fae9458ac634bf7bf8af61ef18f080e808535
Reviewed-on: https://boringssl-review.googlesource.com/7542
Reviewed-by: Steven Valdez <svaldez@google.com>
Reviewed-by: David Benjamin <davidben@google.com>

Uses LCOV for C(++) line coverage and Valgrind's Callgrind tool to
generate assembly-level line coverage for the generated assembly
code.

BUG=590332

Change-Id: Ic70300a272c38f4fa6dd615747db568aa0853584
Reviewed-on: https://boringssl-review.googlesource.com/7251
Reviewed-by: David Benjamin <davidben@google.com>