fix: add RENOVATE_X_IGNORE_RE2 env var to remove warning (#5986)

Renovate has an optional requirement for the RE2 package, and will warn if
it is not present.

Setting env variable RENOVATE_X_IGNORE_RE2=true will hide this warning.
(see renovatebot/renovate#21391)

Dockerfile

@@ -413,6 +413,10 @@ ENV PATH="${PATH}:/node_modules/.bin"
 ENV PATH="${PATH}:/usr/lib/go/bin"
 ENV PATH="${PATH}:${DART_SDK}/bin:/root/.pub-cache/bin"
 
+# Renovate optionally requires re2, and will warn if its not present
+# Setting this envoronment variable disables this warning.
+ENV RENOVATE_X_IGNORE_RE2="true"
+
 # File to store linter versions
 ENV VERSION_FILE="/action/linterVersions.txt"
 RUN mkdir /action

test/inspec/super-linter/controls/super_linter.rb

@@ -18,6 +18,10 @@
     its("content") { should match(/^(standard|slim)$/) }
   end
 
+  describe os_env("RENOVATE_X_IGNORE_RE2") do
+    its("content") { should eq "true" }
+  end
+
   if (image == "standard")
     describe os_env("POWERSHELL_TELEMETRY_OPTOUT") do
       its("content") { should eq "1" }