…voyproxy#415).

Bazel has 3 compilation modes out-of-the-box {fastbuild, opt, dbg}, see
https://bazel.build/versions/master/docs/bazel-user-manual.html#flag--compilation_mode.

The cmake build flags for normal/debug/server_only/asan/coverage are at
envoyproxy#415 (comment).

Below are the relevant flags (ignoring -include etc.) from the various builds. Lines that begin with
* are those that include additional flags we're injecting.

fastbuild:

 -U_FORTIFY_SOURCE -fstack-protector -Wall
 -Wunused-but-set-parameter -Wno-free-nonheap-object -fno-omit-frame-pointer '-std=c++0x'
 -frandom-seed=...
 -fPIC
*-DBAZEL_BRINGUP -Wall -Wextra -Werror -Wnon-virtual-dtor -Woverloaded-virtual
*-Wold-style-cast '-std=c++0x' -includeprecompiled/precompiled.h -DDEBUG
 -fno-canonical-system-headers
 -Wno-builtin-macro-redefined '-D__DATE__="redacted"' '-D__TIMESTAMP__="redacted"'
 '-D__TIME__="redacted"'

dbg:

 -U_FORTIFY_SOURCE -fstack-protector -Wall
 -Wunused-but-set-parameter -Wno-free-nonheap-object -fno-omit-frame-pointer -g '-std=c++0x'
 -frandom-seed=...
 -fPIC
*-DBAZEL_BRINGUP -Wall -Wextra -Werror -Wnon-virtual-dtor
*-Woverloaded-virtual -Wold-style-cast '-std=c++0x' -includeprecompiled/precompiled.h -ggdb3 -DDEBUG
 -fno-canonical-system-headers
 -Wno-builtin-macro-redefined '-D__DATE__="redacted"' '-D__TIMESTAMP__="redacted"'
 '-D__TIME__="redacted"'

opt:

 -U_FORTIFY_SOURCE -fstack-protector -Wall
 -Wunused-but-set-parameter -Wno-free-nonheap-object -fno-omit-frame-pointer -g0 -O2
 '-D_FORTIFY_SOURCE=1' -DNDEBUG -ffunction-sections -fdata-sections '-std=c++0x'
 -frandom-seed=...
*-DBAZEL_BRINGUP -Wall -Wextra -Werror -Wnon-virtual-dtor
*-Woverloaded-virtual -Wold-style-cast '-std=c++0x' -includeprecompiled/precompiled.h
 -fno-canonical-system-headers
 -Wno-builtin-macro-redefined '-D__DATE__="redacted"' '-D__TIMESTAMP__="redacted"'
 '-D__TIME__="redacted"'

This PR requires envoyproxy#716 to merge, since envoyproxy#716 provides some important changes to how the headers are
exported from the 3rd party deps to allow -Wextra and -Wold-style-cast to work.

I've verified that we now have a 100% static envoy-static build, which ldd tells me is not a dynamic
binary.

% bazel build -c opt //source/exe:envoy-static.stripped
Target //source/exe:envoy-static.stripped up-to-date:
  bazel-bin/source/exe/envoy-static.stripped

% ldd bazel-bin/source/exe/envoy-static.stripped
        not a dynamic executable

% ls -lh bazel-bin/source/exe/envoy-static.stripped
 -r-xr-xr-x 1 htuch eng 8.1M Apr  7 15:46 bazel-bin/source/exe/envoy-static.stripped

…ra etc. applying to external dep headers.