Add building information in BUILDING file

BUILDING

@@ -0,0 +1,14 @@
+BUILDING FROM GITHUB:
+=====================
+
+git clone https://github.com/KentBeck/junit.git
+cd junit
+ant dist
+
+BUILDING FROM JARS OR ZIPS:
+===========================
+
+The contents of the zip and jar files are largely maintained for historical
+reasons.  We do not at this time have an official way to build from the src
+jar or zip.  If this is an important missing feature, please let us know
+at http://github.com/KentBeck/junit/issues

build.xml

@@ -168,6 +168,7 @@
       <fileset dir="doc"/>
     </copy>
     <copy file="README.html" tofile="${dist}/README.html" />
+    <copy file="BUILDING" tofile="${dist}/BUILDING" />
     <copy file="cpl-v10.html" tofile="${dist}/cpl-v10.html" />
     <copy file="build.xml" tofile="${dist}/build.xml" />
   </target>

build_tests.sh

@@ -4,6 +4,12 @@ set -o pipefail
 SCRIPT_NAME=$0
 TEST_NAME=${1:-ALL}
 
+function TEST_BUILDING_in_zip {
+  version=$(get_junit_version)
+  ant zip
+  unzip -l junit${version}/junit${version}.zip | grep BUILDING >/dev/null
+}
+
 function TEST_get_junit_version {
   version=$(get_junit_version)
   if [[ ! ($version == 4.*) ]]; then