MNT: FSLDEVDIR doesn't have to exist

etc/fslconf/fsl-devel.sh

@@ -13,15 +13,19 @@
 # FSLCONFDIR contains the FSL Makefile machinery
 # for compiling and installing FSL Makefile-based
 # projects.
-if [ ! -d "$FSLCONFDIR" ]; then
-  export FSLCONFDIR=$FSLDIR/config
+if [ ! -d "${FSLCONFDIR}" ]; then
+  export FSLCONFDIR=${FSLDIR}/config
 fi
 
 # FSLDEVDIR is an optional installation destination
 # for development, so that locally built projects
 # can be installed separately from FSLDIR.
-if [ ! -d "$FSLDEVDIR" ]; then
-  export FSLDEVDIR=$FSLDIR
+#
+# FSLDEVDIR doesn't necessarily have to exist, as
+# it will be created the first time "make install"
+# is run in a project directory.
+if [ -z "${FSLDEVDIR}" ]; then
+  export FSLDEVDIR=${FSLDIR}
 fi
 
 source $FSLDIR/etc/fslconf/fsl.sh