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.

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

Description:

See facebook/openr#28
Closes #10

Differential Revision: D8168516

Pulled By: saifhhasan

fbshipit-source-id: b8185bcc8ba7411254b66e8ed0a9edc9d689efaf

build/build_fbzmq.sh

@@ -241,8 +241,8 @@ apt-get install libdouble-conversion-dev \
   python3-setuptools \
   python-pip
 
-install_glog
 install_gflags
+install_glog # Requires gflags to be build first
 install_gtest
 install_mstch
 install_zstd