Added -lcaliper-tools-util to CMakeLists pkg-config file

[sampollard]

I added -lcaliper-tools-util so someone can more easily link to Caliper via something like

g++ $(pkg-config --cflags --libs-only-L caliper) file.cpp $(pkg-config --libs-only-l caliper)

I'm just now discovering pkg-config so I'm not sure if this is the best way to handle this issue.

[codecov-io]

Codecov Report

Merging #128 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master    #128   +/-   ##
======================================
  Coverage    73.6%   73.6%           
======================================
  Files         111     111           
  Lines        7220    7220           
======================================
  Hits         5314    5314           
  Misses       1906    1906

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