ICU-22257 Add "Test ICU4J with only little-endian ICU4C data"

Automate "Test ICU4J with only little-endian ICU4C data" as stated in
https://unicode-org.github.io/icu/processes/release/tasks/integration.html#test-icu4j-with-only-little-endian-icu4c-data

Update .ci-builds/.azure-exhaustive-tests.yml

Co-authored-by: Markus Scherer <markus.icu@gmail.com>

.ci-builds/.azure-exhaustive-tests.yml

@@ -71,4 +71,34 @@ jobs:
         CC: clang
         CXX: clang++
 #-------------------------------------------------------------------------
-
+# Based on https://unicode-org.github.io/icu/processes/release/tasks/integration.html#test-icu4j-with-only-little-endian-icu4c-data
+- job: ICU4J_with_only_little_endian_ICU4C_data
+  displayName: 'CJ: ICU4J Linux Clang Tests little-endian ICU4C data (Ubuntu 18.04)'
+  timeoutInMinutes: 50
+  pool:
+    vmImage: 'ubuntu-18.04'
+    demands: ant
+  steps:
+    - checkout: self
+      lfs: true
+      fetchDepth: 10
+    - script: |
+        cd icu4c/source && ICU_DATA_BUILDTOOL_OPTS=--include_uni_core_data ./runConfigureICU Linux && make -j 6 check
+      displayName: 'Build ICU4C with ICU_DATA_BUILDTOOL_OPTS'
+      env:
+        CC: clang
+        CXX: clang++
+    - script: |
+        mkdir -p /tmp/icu4j_data_test && cp icu4c/source/data/out/tmp/icudt*l.dat /tmp/icu4j_data_test
+      displayName: 'Copy ICU4C data'
+    - script: |
+        echo "test ICU4J" && cd icu4j && ant init && ant -Dicu4c.data.path=/tmp/icu4j_data_test check
+      displayName: 'Build and Test ICU4J with little-endian data'
+      env:
+        BUILD: ICU4J
+# exit with a non-zero status in order to make this step show as a red X in the UI.
+    - script: |
+        [ -d icu4j/out/junit-results ] && cd icu4j && cat `find out/junit-results -name "*.txt" -exec grep -l FAILED {} \;` && exit 1
+      condition: failed() # only run if the build fails.
+      displayName: 'List failures (if any)'
+#-------------------------------------------------------------------------