Update README.md to install build tool

[xabxx]

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

Merging #44 into master will decrease coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master      #44      +/-   ##
==========================================
- Coverage   81.36%   81.33%   -0.04%     
==========================================
  Files          11       11              
  Lines         365      375      +10     
==========================================
+ Hits          297      305       +8     
- Misses         68       70       +2

Flag	Coverage Δ
#ROS_1	81.33% <ø> (-0.04%)	⬇️
#ROS_2	81.23% <ø> (?)
#dashing	81.23% <ø> (?)
#kinetic	81.36% <ø> (ø)	⬆️
#melodic	81.23% <ø> (?)

Impacted Files	Coverage Δ
...on/include/aws_common/sdk_utils/parameter_reader.h	62.5% <0%> (-8.93%)	⬇️
...ws_common/src/sdk_utils/logging/aws_log_system.cpp	92.85% <0%> (-1.43%)	⬇️
...rc/sdk_utils/auth/service_credentials_provider.cpp	84.53% <0%> (+0.08%)	⬆️
.../include/aws_common/sdk_utils/throttling_manager.h	95.23% <0%> (+0.23%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 51f339e...875b78a. Read the comment docs.