(PDK-1088) Remove unnecessary file enumeration loop during PDK build

[scotje]

Prior to this change, every call to PDK::Module::Build#ignored_files
resulted in a Find.find enumeration of the entire module tree to test
whether or not the target_dir should be added to the ignored_files
PathSpec.

The fundamental issue was that this enumeration happened on
every call when it should have been cached after the first call, but I
also refactored the check itself to use File.realdirpath and simple
string comparisons.

Before:

PS>Measure-Command { bundle exec pdk build --force | Out-Default }
pdk (INFO): Building puppetlabs-windows version 5.0.0
[*] Cleaning up after running unit tests.
pdk (INFO): Build of puppetlabs-windows has completed successfully. Built package can be found here: C:/Users/pdk-dev/sandbox/puppetlabs-windows/pkg/puppetlabs-windows-5.0.0.tar.gz


Days              : 0
Hours             : 0
Minutes           : 1
Seconds           : 21
Milliseconds      : 272
Ticks             : 812723994
TotalDays         : 0.000940652770833333
TotalHours        : 0.0225756665
TotalMinutes      : 1.35453999
TotalSeconds      : 81.2723994
TotalMilliseconds : 81272.3994

After:

PS>Measure-Command { bundle exec pdk build --force | Out-Default }
pdk (INFO): Building puppetlabs-windows version 5.0.0
[*] Cleaning up after running unit tests.
pdk (INFO): Build of puppetlabs-windows has completed successfully. Built package can be found here: C:/Users/pdk-dev/sandbox/puppetlabs-windows/pkg/puppetlabs-windows-5.0.0.tar.gz


Days              : 0
Hours             : 0
Minutes           : 0
Seconds           : 15
Milliseconds      : 444
Ticks             : 154443436
TotalDays         : 0.000178753976851852
TotalHours        : 0.00429009544444444
TotalMinutes      : 0.257405726666667
TotalSeconds      : 15.4443436
TotalMilliseconds : 15444.3436

[scotje]

cc @glennsarti

[scotje]

@rodjek Think we can sneak this into 1.6.1?

[coveralls]

Coverage remained the same at 92.807% when pulling 52b9629 on scotje:1088_fix_slow_build into 962d71d on puppetlabs:master.

[rodjek]

🤦‍♂️