Add GLog installation step for Ubuntu and CentOS

[sevar83]

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[sevar83]

@googlebot I signed it!

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[mgyong]

@jiuqiant @chuoling Our first pull request. Pls take a look

[mgyong]

@sevar83 Glog is compiled into standard MediaPipe biinary. As such, we don't need sudo apt-get install libgoogle-glog-dev

[sevar83]

Hmm, I had a build error about this dependency and I'm sure after I installed it myself the build completed.

…

On Mon, Aug 26, 2019, 22:21 Ming Yong ***@***.***> wrote: @sevar83 <https://github.com/sevar83> Glog is already installed as part of the standard MediaPipe install. As such, we don't need sudo apt-get install libgoogle-glog-dev — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#48>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAA5FVKSJORQKLVN7AUW3YTQGQULHANCNFSM4IPG3S4A> .

[mgyong]

@sevar83 hmm. I tried a fresh linux install and got it built without error. You need to run the export line below export GLOG_logtostderr=1 before you can see the output printing Hello World!
I will close out this pull request for now. Pls reopen it if you are able to repeat this issue