Remove the magic that sets CXX in the toplevel Makefile

Remove the magic that sets CXX in the toplevel Makefile

The logic was supposed to trigger a rebuild if the CXX variable is
changed. However, it failed to track the other compiler related
variables, and, what is worse, conflicted with the clang=1 gyp setting
by forcing CXX to g++

The new logic just relies on tracking GYP defines, and checks whether
the CXX binary - if set - has a target different from the host
architecture.

BUG=none
R=jkummerow@chromium.org
LOG=n

Committed: https://crrev.com/fdf6777072db5927b4e05bd93485b6a5d1951027
Cr-Commit-Position: refs/heads/master@{#25973}

[Jakob Kummerow, 2015-01-07 13:02:05]

LGTM with comment.

https://codereview.chromium.org/807143003/diff/1/Makefile
File Makefile (right):

https://codereview.chromium.org/807143003/diff/1/Makefile#newcode148
Makefile:148: export ASAN_SYMBOLIZER_PATH=$(dir $(asan))llvm-symbolizer
This ain't gonna work no more. If you can't fix it, kill it.

[jochen (gone - plz use gerrit), 2015-01-07 13:05:51]

The CQ bit was checked by jochen@chromium.org

[commit-bot: I haz the power, 2015-01-07 13:06:27]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/807143003/20001

[commit-bot: I haz the power, 2015-01-07 13:33:14]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-01-07 13:33:28]

Patchset 2 (id:??) landed as
https://crrev.com/fdf6777072db5927b4e05bd93485b6a5d1951027
Cr-Commit-Position: refs/heads/master@{#25973}