Tweak error handling for device script functions.

[ashthespy]

Building upon the discussion in db7b9568d6b7115d39086b3ea4311bedb99cb4c9, tweaked the error handling for our device template functions. Errors in device_chroot_xxx device functions were caught previously because chroot would propagate any error up catch the trap. But device functions like write_device_xx wouldn't given the way Bash handles functions environments by default. We now set the -o errtrace flag to explicitly force errors in functions to catch traps as well.

Also tried to have the errors be a little more informative to quickly track down where they arise. The stack trace is quite rudimentary - it isn't the best (even worse inside chroot), but it is something ;-)

Some tests:

diff --git a/recipes/devices/families/kvims.sh b/recipes/devices/families/kvims.sh
index 2834189..d20c32c 100644
--- a/recipes/devices/families/kvims.sh
+++ b/recipes/devices/families/kvims.sh
@@ -50,6 +50,9 @@ write_device_files() {
   rm "${ROOTFSMNT}/boot/aml_autoscript"
   rm "${ROOTFSMNT}/boot/aml_autoscript.cmd"

+  log "Testing error traps"
+  cp "this/path/should/throw/an/error" "${ROOTFSMNT}/boot"
+
   log "Retain copies of u-boot files for Volumio Updater"
   cp -r "${PLTDIR}/${DEVICEBASE}/uboot" "${ROOTFSMNT}/boot"
   cp -r "${PLTDIR}/${DEVICEBASE}/uboot-mainline" "${ROOTFSMNT}/boot"

[ .... ] Copying Volumio rootfs  
[ .. ] Creating Volumio Temp Directory 
[ .. ] Creating mount point for the images partition 
[ .... ] Copying Volumio RootFs  
[ .... ] Getting device specific files for mp1 from platform-khadas  
[ .. ] Platform folder exists, keeping it [ platform-khadas ]
[ .... ] Copying mp1 boot files from platform-khadas/vims.tar.xz  
[ cfg ] Entering write_device_files 
[ .. ] Running write_device_files [ ext ]
[ .. ] AML autoscripts not for Volumio 
[ .. ] Testing error traps 
cp: cannot stat 'this/path/should/throw/an/error': No such file or directory
[ error ] Imagebuilder script failed!! 
[ error ] Error stack [write_device_files] <= [source] <= [main] <=  [ 53 /Build/recipes/devices/families/kvims.sh ]
[ .. ] Cleaning up image_tmp mounts 
[ .. ] Cleaning loop device /dev/loop26 [ /dev/loop26: [2065]:2109151 (/Build/Build_2021-01-11_15-56-33/Volumio-0.00-2021-01-11-mp1.img) ]
[ .. ] Deleting image file 

And inside chroot

diff --git a/recipes/devices/families/kvims.sh b/recipes/devices/families/kvims.sh
index 2834189..4eb8c67 100644
--- a/recipes/devices/families/kvims.sh
+++ b/recipes/devices/families/kvims.sh
@@ -124,6 +124,8 @@ device_image_tweaks() {
 # Will be run in chroot - Pre initramfs
 device_chroot_tweaks_pre() {
   log "Performing device_chroot_tweaks_pre" "ext"
+  log "Testing error traps (chroot)"
+  cp "this/path/should/throw/an/erro/inside/chroot" "${ROOTFSMNT}/boot"

   log "Creating boot parameters from template"
   sed -i "s/#imgpart=UUID=/imgpart=UUID=${UUID_IMG}/g" /boot/env.system.txt

Setting up bluez-obexd (5.50-1.2~deb10u1) ...
Processing triggers for mime-support (3.62) ...
Processing triggers for hicolor-icon-theme (0.17-2) ...
Processing triggers for libc-bin (2.28-10) ...
Processing triggers for systemd (241-7~deb10u5) ...
Processing triggers for dbus (1.12.20-0+deb10u1) ...
[ cfg ] Entering device_chroot_tweaks_pre 
[ .. ] Performing device_chroot_tweaks_pre [ ext ] 
[ -- ] Testing error traps (chroot)  
/bin/cp: cannot stat 'this/path/should/throw/an/erro/inside/chroot': No such file or directory
[ error ] Volumio chroot config failed [ chrootconfig.sh ]
[ error ] Error stack [device_chroot_tweaks_pre] <= [main] <=  [ 21 /chroot_device_config.sh ]
[ error ] Imagebuilder script failed!! 
[ error ] Error stack [source] <= [main] <=  [ 218 /Build/scripts/makeimage.sh ]
[ -- ] Cleaning up image_tmp mounts 
[ -- ] Unmounting chroot temporary devices at /mnt/volumio/rootfs 
[ .. ] Cleaning loop device /dev/loop26 [ /dev/loop26: [2065]:2109153 (/Build/Build_2021-01-11_15-58-36/Volumio-0.00-2021-01-11-mp1.img) ]
[ .. ] Deleting image file