Don't pass OPENSHIFT_IP env variable when building old BWC branches (#50153)

This commit tweaks the workaround introduced in #49211 to support
Gradle 6.0. In the workaround, we specifically override the address
the Gradle daemon binds to by passing the desired address via the
OPENSHIFT_IP environment variable. This works fine for builds using
Gradle 6.0, but for older Gradle versions this causes issues with
inter-daemon communication, specifically when we build BWC branches
not on Gradle 6.0. The fix here is to strip that environment variable
out when building the target BWC branch if that branch is on an
older Gradle version.

This is all temporary and will be removed when this bug fix is released
in Gradle 6.1.

Closes #50025

distribution/bwc/build.gradle

@@ -23,6 +23,7 @@ import org.elasticsearch.gradle.Version
 import org.elasticsearch.gradle.BwcVersions
 import org.elasticsearch.gradle.info.BuildParams
 import org.elasticsearch.gradle.info.GlobalBuildInfoPlugin
+import org.gradle.util.GradleVersion
 
 import java.nio.charset.StandardCharsets
 
@@ -161,6 +162,12 @@ bwcVersions.forPreviousUnreleased { BwcVersions.UnreleasedVersionInfo unreleased
         spoolOutput = true
         workingDir = checkoutDir
         doFirst {
+          // TODO: Remove this once we've updated to Gradle 6.1
+          // Workaround for https://github.com/gradle/gradle/issues/11426
+          if (GradleVersion.version(file("${ checkoutDir}/buildSrc/src/main/resources/minimumGradleVersion").text) != GradleVersion.current()) {
+            environment = environment.findAll { key, val -> key != 'OPENSHIFT_IP' }
+          }
+
           // Execution time so that the checkouts are available
           List<String> lines = file("${checkoutDir}/.ci/java-versions.properties").readLines()
           environment(