misc shellcheck fixes

bin/kaleidoscope-builder

@@ -196,10 +196,10 @@ find_sketch () {
 
 
 find_device_vid_pid() {
-    : ${VID:=$(get_arduino_pref 'build.vid')}
-    : ${SKETCH_PID:=$(get_arduino_pref 'build.pid')}
-    : ${BOOTLOADER_PID:=$(get_arduino_pref 'bootloader.pid')}
-    : ${BOOTLOADER_VID:=$(get_arduino_pref 'bootloader.vid')}
+    : "${VID:=$(get_arduino_pref 'build.vid')}"
+    : "${SKETCH_PID:=$(get_arduino_pref 'build.pid')}"
+    : "${BOOTLOADER_PID:=$(get_arduino_pref 'bootloader.pid')}"
+    : "${BOOTLOADER_VID:=$(get_arduino_pref 'bootloader.vid')}"
 }
 
 
@@ -460,8 +460,8 @@ do_compile () {
 get_arduino_pref() {
         pref=$1
         # Strip the preference name. And then strip leading and trailing quotations
-        MESSAGE=$(dump_arduino_prefs | grep --max-count=1 ${pref}= | sed -e s/^.*${pref}=// -e 's/^"//' -e 's/"$//')
-        echo $MESSAGE
+        MESSAGE=$(dump_arduino_prefs | grep --max-count=1 "${pref}=" | sed -e s/^.*${pref}=// -e 's/^"//' -e 's/"$//')
+        echo "$MESSAGE"
 }