Fix glog command line arguments on a clean build

Summary:
To support glog's command line arguments like --logtostderr, it requires gflags.

If gflags is not found, glog will still compile but the command line arguments will be absent.

As glog was created before gflags, that was the case on a clean build.
Note that on subsequent builds gflags already existed, so a second build 'magically' made the command line arguments appear.

Pull Request Template
Title: glog flags like --logtostderr are missing on a clean build

Description:

See #28
Closes #29

Differential Revision: D8168498

Pulled By: saifhhasan

fbshipit-source-id: 419f29a6c103cfecd38693fa66187568bbe9c3f9

build/build_openr.sh

@@ -316,8 +316,8 @@ sudo apt-get install -y libdouble-conversion-dev \
 # install other dependencies from source
 #
 
-install_glog
 install_gflags
+install_glog # Requires gflags to be build first
 install_gtest
 install_mstch
 install_zstd