We've historically represented compile_flags as a single line, ex:

compile_flags: --dbg=on --opt=on -j$(grep -c ^processor /proc/cpuinfo) --link-model=dynamic --variables-files=etc/scons/mongodbtoolchain_testing_gcc.vars 

but it's way more readable to list them using YAML's vertical style blocks:

compile_flags: >-
  --dbg=on 
  --opt=on 
  -j$(grep -c ^processor /proc/cpuinfo) 
  --link-model=dynamic
  --variables-files=etc/scons/mongodbtoolchain_testing_gcc.vars 

This ticket represents making a bulk change to all compile_flags expansions. This can also apply to a number of other expansions: csfle_task_compile_flags, task_compile_flags, test_flags, burn_in_tag_buildvariants, additional_package_targets