Upgrade AWS CPP SDK Version for WebRTC-C Canary

[stefankiesz]

Changes

Updates AWS CPP SDK version from 1.9.67 to 1.11.143 in WebRTC-C Canary.

• CMAKE_PREFIX_PATH is now set, and it is set to the dependency build directory /build/_deps
  • This solved undefined reference to 'EVP_idea_cbc@OPENSSL_1_1_0' errors associated with the following warning by directly specifying which directory to search in for dependencies.

Cannot generate a safe runtime search path for target [...] because files in some directories
may conflict with libraries in implicit directories:
    runtime library [libcrypto.so.1.1] in /usr/lib/x86_64-linux-gnu may be hidden by files in:
      /home/ubuntu/amazon-kinesis-video-streams-demos/canary/webrtc-c/build/_deps/webrtc-src/open-source/lib
Some of these libraries may not be found correctly.  

• /build/_deps/lib is then added to link_directories to point to the dependency libraries, preventing the following errors:

/usr/bin/ld: cannot find -lkvspicUtils
/usr/bin/ld: cannot find -lkvsCommonLws
/usr/bin/ld: cannot find -lwebsockets

Testing

These changes have been tested by successfully running cmake, make, and ./kvsWebrtcCanaryWebrtc and then verifying that metrics are emitting to CloudWatch.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[sirknightj]

Thoughts on bumping this all the way to most recent?