re-invent a form of debug logging via JARS_DEBUG=true

[kares]

one of the things we lost switching to Mima (#102)

old logging example: https://gist.github.com/kares/5186c2d792bf6032cc04c431b88cc1f9

this new logging isn't that detailed but hopefully still quite useful:

JARS_DEBUG=true ruby -Ilib -rjar_dependencies -S gem install psych
--- loaded jars ---
	
jar registration: ["org.bouncycastle", "bcprov-jdk18on", "1.84"]; loaded=true
jar registration: ["org.bouncycastle", "bcpkix-jdk18on", "1.84"]; loaded=true
jar registration: ["org.bouncycastle", "bcutil-jdk18on", "1.84"]; loaded=true
jar registration: ["org.bouncycastle", "bctls-jdk18on", "1.84"]; loaded=true
jar registration: ["org.snakeyaml", "snakeyaml-engine", "2.10"]; loaded=true
Fetching psych-5.4.0-java.gem
  jar dependencies for psych-5.4.0-java.gemspec . . .
[mima] resolving artifact org.snakeyaml:snakeyaml-engine:pom:2.10
[mima] downloading artifact org.snakeyaml:snakeyaml-engine:pom:2.10 from central (https://repo.maven.apache.org/maven2/, default, releases)
[mima] transfer initiated get https://repo.maven.apache.org/maven2/org/snakeyaml/snakeyaml-engine/2.10/snakeyaml-engine-2.10.pom
[mima] transfer started get https://repo.maven.apache.org/maven2/org/snakeyaml/snakeyaml-engine/2.10/snakeyaml-engine-2.10.pom
[mima] transfer succeeded get https://repo.maven.apache.org/maven2/org/snakeyaml/snakeyaml-engine/2.10/snakeyaml-engine-2.10.pom (22.6 KB)
[mima] downloaded artifact org.snakeyaml:snakeyaml-engine:pom:2.10 -> /home/kares/.m2/repository/org/snakeyaml/snakeyaml-engine/2.10/snakeyaml-engine-2.10.pom
[mima] resolved artifact org.snakeyaml:snakeyaml-engine:pom:2.10 -> /home/kares/.m2/repository/org/snakeyaml/snakeyaml-engine/2.10/snakeyaml-engine-2.10.pom
[mima] resolving artifact org.snakeyaml:snakeyaml-engine:jar:2.10
[mima] downloading artifact org.snakeyaml:snakeyaml-engine:jar:2.10 from central (https://repo.maven.apache.org/maven2/, default, releases)
[mima] transfer initiated get https://repo.maven.apache.org/maven2/org/snakeyaml/snakeyaml-engine/2.10/snakeyaml-engine-2.10.jar
[mima] transfer started get https://repo.maven.apache.org/maven2/org/snakeyaml/snakeyaml-engine/2.10/snakeyaml-engine-2.10.jar
[mima] transfer succeeded get https://repo.maven.apache.org/maven2/org/snakeyaml/snakeyaml-engine/2.10/snakeyaml-engine-2.10.jar (293.0 KB)
[mima] downloaded artifact org.snakeyaml:snakeyaml-engine:jar:2.10 -> /home/kares/.m2/repository/org/snakeyaml/snakeyaml-engine/2.10/snakeyaml-engine-2.10.jar
[mima] resolved artifact org.snakeyaml:snakeyaml-engine:jar:2.10 -> /home/kares/.m2/repository/org/snakeyaml/snakeyaml-engine/2.10/snakeyaml-engine-2.10.jar
Successfully installed psych-5.4.0-java
1 gem installed