Updated script to create .hgtip after getting jdk (#2036)

Signed-off-by: Austin Bailey <Austin.Bailey@ibm.com>

sbin/prepareWorkspace.sh

@@ -103,6 +103,8 @@ checkoutAndCloneOpenJDKGitRepo() {
 
   updateOpenj9Sources
 
+  createSourceTagFile
+
   cd "${BUILD_CONFIG[WORKSPACE_DIR]}"
 }
 
@@ -628,6 +630,25 @@ applyPatches() {
   fi
 }
 
+# jdk8u requires a .hgtip file to populate the "SOURCE" tag in the release file.
+# Creates .hgtip and populates it with the git sha of the last commit(s).
+createSourceTagFile(){
+  if [ "${BUILD_CONFIG[OPENJDK_CORE_VERSION]}" == "${JDK8_CORE_VERSION}" ]; then
+    local OpenJDK_TopDir="${BUILD_CONFIG[WORKSPACE_DIR]}/${BUILD_CONFIG[WORKING_DIR]}/${BUILD_CONFIG[OPENJDK_SOURCE_DIR]}"
+    local OpenJDK_SHA=$(git -C $OpenJDK_TopDir rev-parse --short HEAD)
+    if [ "${BUILD_CONFIG[BUILD_VARIANT]}" == "${BUILD_VARIANT_OPENJ9}" ]; then
+      # OpenJ9 list 3 SHA's in their release file: OpenJDK, OpenJ9, and OMR.
+      local OpenJ9_TopDir="$OpenJDK_TopDir/openj9"
+      local OMR_TopDir="$OpenJDK_TopDir/omr"
+      local OpenJ9_SHA=$(git -C $OpenJ9_TopDir rev-parse --short HEAD)
+      local OMR_SHA=$(git -C $OMR_TopDir rev-parse --short HEAD)
+      (printf "OpenJDK: %s OpenJ9: %s OMR: %s" $OpenJDK_SHA $OpenJ9_SHA $OMR_SHA) > $OpenJDK_TopDir/.hgtip
+    else # Other variants only list the main repo SHA.
+      (printf "OpenJDK: %s" $OpenJDK_SHA) > $OpenJDK_TopDir/.hgtip
+    fi
+  fi
+}
+
 ##################################################################
 
 function configureWorkspace() {