Don't honor VERSION_QUALIFIER if set but empty (#17032)

PR #17006 revealed that the `VERSION_QUALIFIER` env var gets honored in
various scripts when present but empty.
This shouldn't be the case as the DRA process is designed to gracefully
ignore empty values for this variable.

This commit changes various ruby scripts to not treat "" as truthy.
Bash scripts (used by CI etc.) are already ok with this as part of
refactorings done in #16907.

---------

Co-authored-by: Andrea Selva <selva.andre@gmail.com>

logstash-core-plugin-api/logstash-core-plugin-api.gemspec

@@ -13,7 +13,7 @@ if File.exist?(project_versions_yaml_path)
   # each time we build the logstash-core gem
   original_lines = IO.readlines(project_versions_yaml_path)
   # introduce the version qualifier (e.g. beta1, rc1) into the copied yml so it's displayed by Logstash
-  if ENV['VERSION_QUALIFIER']
+  unless ENV['VERSION_QUALIFIER'].to_s.strip.empty?
     logstash_version_line = original_lines.find {|line| line.match(/^logstash:/) }
     logstash_version_line.chomp!
     logstash_version_line << "-#{ENV['VERSION_QUALIFIER']}\n"

logstash-core/logstash-core.gemspec

@@ -18,7 +18,7 @@ if File.exist?(project_versions_yaml_path)
   # each time we build the logstash-core gem
   original_lines = IO.readlines(project_versions_yaml_path)
   # introduce the version qualifier (e.g. beta1, rc1) into the copied yml so it's displayed by Logstash
-  if ENV['VERSION_QUALIFIER']
+  unless ENV['VERSION_QUALIFIER'].to_s.strip.empty?
     logstash_version_line = original_lines.find {|line| line.match(/^logstash:/) }
     logstash_version_line.chomp!
     logstash_version_line << "-#{ENV['VERSION_QUALIFIER']}\n"

qa/docker/spec/spec_helper.rb

@@ -13,7 +13,7 @@ def version
 end
 
 def qualified_version
-  qualifier = ENV['VERSION_QUALIFIER']
+  qualifier = ENV['VERSION_QUALIFIER'].to_s.strip.empty? ? nil : ENV['VERSION_QUALIFIER']
   qualified_version = qualifier ? [version, qualifier].join("-") : version
   ENV["RELEASE"] == "1" ? qualified_version : [qualified_version, "SNAPSHOT"].join("-")
 end

rakelib/artifacts.rake

@@ -17,7 +17,7 @@
 
 namespace "artifact" do
   SNAPSHOT_BUILD = ENV["RELEASE"] != "1"
-  VERSION_QUALIFIER = ENV["VERSION_QUALIFIER"]
+  VERSION_QUALIFIER = ENV["VERSION_QUALIFIER"].to_s.strip.empty? ? nil : ENV["VERSION_QUALIFIER"]
   LOCAL_ARTIFACTS = ENV["LOCAL_ARTIFACTS"] || "true"
   PACKAGE_SUFFIX = SNAPSHOT_BUILD ? "-SNAPSHOT" : ""