When running "make help" in a fresh configuration, or after a clean, the output looks like this:

make[1]: Entering directory `/localhome/hg/jdk9-dev'
/bin/mkdir -p /localhome/hg/jdk9-dev/build/linux-x86_64-normal-server-release/make-support/bt_classes_moduleslist
/bin/rm -f /localhome/hg/jdk9-dev/build/linux-x86_64-normal-server-release/make-support/bt_classes_moduleslist/_the.BUILD_GENMODULESLIST_batch /localhome/hg/jdk9-dev/build/linux-x86_64-normal-server-release/make-support/bt_classes_moduleslist/_the.BUILD_GENMODULESLIST_batch.tmp
/bin/echo > /dev/null Writing 5 paths to ' >> /localhome/hg/jdk9-dev/build/linux-x86_64-normal-server-release/make-support/bt_classes_moduleslist/_the.BUILD_GENMODULESLIST_batch.tmp'
/bin/echo Compiling `/usr/bin/wc /localhome/hg/jdk9-dev/build/linux-x86_64-normal-server-release/make-support/bt_classes_moduleslist/_the.BUILD_GENMODULESLIST_batch.tmp | /usr/bin/tr -s ' ' | /usr/bin/cut -f 2 -d ' '` files for BUILD_GENMODULESLIST
Compiling 5 files for BUILD_GENMODULESLIST
( (/bin/bash /localhome/hg/jdk9-dev/common/bin/logger.sh /localhome/hg/jdk9-dev/build/linux-x86_64-normal-server-release/make-support/bt_classes_moduleslist/_the.BUILD_GENMODULESLIST_batch.log /localhome/java/default/bin/javac -XDignore.symbol.file=true -g -Xlint:all,-deprecation -Werror -implicit:none -d /localhome/hg/jdk9-dev/build/linux-x86_64-normal-server-release/make-support/bt_classes_moduleslist @/localhome/hg/jdk9-dev/build/linux-x86_64-normal-server-release/make-support/bt_classes_moduleslist/_the.BUILD_GENMODULESLIST_batch.tmp && /bin/rm -f /localhome/hg/jdk9-dev/build/linux-x86_64-normal-server-release/make-support/bt_classes_moduleslist/_the.BUILD_GENMODULESLIST_batch.log) || (exitcode=$? && /bin/mv /localhome/hg/jdk9-dev/build/linux-x86_64-normal-server-release/make-support/bt_classes_moduleslist/_the.BUILD_GENMODULESLIST_batch.log /localhome/hg/jdk9-dev/build/linux-x86_64-normal-server-release/make-support/failure-logs/BUILD_GENMODULESLIST.log && exit $exitcode) ) && /bin/mv /localhome/hg/jdk9-dev/build/linux-x86_64-normal-server-release/make-support/bt_classes_moduleslist/_the.BUILD_GENMODULESLIST_batch.tmp /localhome/hg/jdk9-dev/build/linux-x86_64-normal-server-release/make-support/bt_classes_moduleslist/_the.BUILD_GENMODULESLIST_batch
/localhome/java/default/bin/java -XX:+UseSerialGC -Xms32M -Xmx512M -cp "/localhome/hg/jdk9-dev/build/linux-x86_64-normal-server-release/make-support/bt_classes_moduleslist" build.tools.module.GenModulesList -o /localhome/hg/jdk9-dev/build/linux-x86_64-normal-server-release/make-support/modules.list /localhome/hg/jdk9-dev/modules.xml /localhome/hg/jdk9-dev/closed/modules.xml /localhome/hg/jdk9-dev/deploy/modules.xml
/bin/cat /localhome/hg/jdk9-dev/build/linux-x86_64-normal-server-release/make-support/modules.list | /bin/sed -e 's/^\([^:]*\):/DEPS_\1 :=/g' > /localhome/hg/jdk9-dev/build/linux-x86_64-normal-server-release/make-support/module-deps.gmk
make[1]: Leaving directory `/localhome/hg/jdk9-dev'
make[1]: Entering directory `/localhome/hg/jdk9-dev'
make[1]: Leaving directory `/localhome/hg/jdk9-dev'

OpenJDK Makefile help
=====================
...

This looks like the initialization procedure is running with command line echoing turned on.