Fix gflag namespace of example and tools #1643

Job	Run time
gcc-compile-with-cmake	3m 9s
gcc-compile-with-cmake	3m 9s
gcc-compile-with-cmake-all-options	2m 47s
gcc-compile-with-cmake-all-options	5m 18s
gcc-compile-with-boringssl	17m 57s
gcc-compile-with-boringssl	17m 57s
gcc-compile-with-bazel	16m 41s
gcc-compile-with-bazel	16m 41s
gcc-compile-with-make	2m 47s
gcc-compile-with-make	2m 47s
gcc-compile-with-make-all-options	2m 48s
gcc-compile-with-make-all-options	5m 6s
clang-compile-with-bazel	15m 52s
clang-compile-with-bazel	15m 52s
clang-compile-with-bazel-all-options	16m 48s
clang-compile-with-bazel-all-options	16m 48s
clang-compile-with-boringssl	16m 59s
clang-compile-with-boringssl	16m 59s
clang-compile-with-cmake	2m 42s
clang-compile-with-cmake	2m 42s
clang-compile-with-cmake-all-options	4m 45s
clang-compile-with-cmake-all-options	4m 45s
clang-compile-with-make	2m 50s
clang-compile-with-make	2m 50s
clang-compile-with-make-all-options	5m 18s
clang-compile-with-make-all-options	5m 18s
gcc-compile-with-bazel-all-options	18m 1s
gcc-compile-with-bazel-all-options	18m 1s
clang-unittest	16m 19s
clang-unittest	16m 19s
	4h 56m 15s

Provide feedback