[RelEng] Fix determination of baseline drop for first promotions

The removal of the just promoted drop must happen before check if the
list of baseline drops is empty. Otherwise for the first promotion of a
release cycle (usually M1) that check is useless.

Follow-up on
- #3651

Author: HannesWell

JenkinsJobs/Releng/promoteBuild.jenkinsfile

@@ -151,10 +151,10 @@ pipeline {
 						renameBuildDrop('eclipse/downloads/drops4', "${DROP_ID}", "${BUILD_LABEL}", "${DL_DROP_ID}", "${DL_LABEL}") { buildProperties ->
 							script {
 								def baselineBuilds = utilities.listBuildDropDirectoriesOnRemote("${EP_ROOT}/eclipse/downloads/drops4", "${DL_TYPE}*") // sorted in ascending order
+								baselineBuilds.remove(env.DL_DROP_ID) // ignore the just promoted drop when determining the latest
 								if (baselineBuilds.isEmpty() && "${DL_TYPE}" == 'S') { // For M1 usually no previous stable build exists
 									baselineBuilds = utilities.listBuildDropDirectoriesOnRemote("${EP_ROOT}/eclipse/downloads/drops4", 'R*')
 								}
-								baselineBuilds.remove(env.DL_DROP_ID) // ignore the just promoted drop when determining the latest
 								buildProperties.gitTag = env.GIT_TAG
 								buildProperties.gitBaselineTag = utilities.stableBuildGitTag("${baselineBuilds.last()}")
 								echo "gitTag: ${buildProperties.gitTag}, gitBaselineTag: ${buildProperties.gitBaselineTag}"