Instrumented libraries: move build-flags-related logic to the GYP file.

- Keep both the general and package-specific CFLAGS/LDFLAGS in the GYP file, and
pass only the final flags to the script. This allows us to simplify things
somewhat, as well as easily change the build flags based on GYP defines.
- Consequently, the global msan_track_origins GYP flag now also affects
instrumented libraries.
- I also threw in a mass renaming "library" -> "package".

BUG=313751
R=glider@chromium.org
NOTRY=true
TEST=MSan

Review URL: https://codereview.chromium.org/337613008

Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: def451e3a6164e43e21014619933aab386f2ed44
4 files changed