Your Makefile works for me (with spaces replaced by tabs), so it sounds like you have a case of random characters without printing.
Try checking the " cat -vet Makefile" output . This will show where EOL, TAB and other invisible characters.
You need to see something like this:
$
BACKUP_ROOT = /srv/backup$
ETC_PATH = /srv/config$
SVN_PATH = /srv/svn/$
TRAC_PATH = /srv/trac/sysinventory$
PR10_PATH = /swsd/project/vmimages/...$
PR10_MOUNT_PATH = /tmp/temp_sshfs_pr10$
$
MYSQL_USER = "xxx"$
MYSQL_PASSWORD = "xxx"$
$
$
DATE = `date +%F`$
$
help :$
^Icat README$
$
$
init-environment :$
^Imkdir -p $(BACKUP_ROOT)$
^Imkdir $(BACKUP_ROOT)/tmp$
^Imkdir -p $(PR10_MOUNT_PATH)$
$
Make sure that " ^I" precedes all commands .
, - :
cat -vet Makefile | grep "\^[^I]" --colour=auto