Blind attempt to clean up 630_run_efibootmgr.sh (issue 1942)

[jsmeix]

• Type: Enhancement Cleanup

• Impact: Normal

• Reference to related issue (URL):
  Support EFISTUB booting (e.g. on Arch Linux) #1942

• How was this pull request tested?
  Not at all because currently I do not use UEFI on my test systems

• Brief description of the changes in this pull request:
  A blind cleanup attempt by plain looking at the code
  which is intended as a proposal how I think 630_run_efibootmgr.sh
  could be enhanced and cleaned up in general:

Determine the ESP mountpoint from the UEFI_BOOTLOADER value
and use $TARGET_FS_ROOT/boot/efi as fallback so that there is
(hopefully) no longer the need to error out.

Corrected the logic at the end whether or not NOBOOTLOADER is set empty.

Skip what it does when UEFI_BOOTLOADER is empty or not a regular file.

A bit more verbose messages what is going on.

[gozora]

Cloning this right ahead and use it for my upcoming tests.
I'll keep you posted.

V.

[gozora]

I've used new version several times, while working on EFISTUB support and it works good!
With old code:

[[ -d "$TARGET_FS_ROOT/boot/efi" ]]
StopIfError "Could not find directory $TARGET_FS_ROOT/boot/efi"

EFISTUB will just end with error ...

V.

[jsmeix]

Approved blind attempts of me get merged istantly by me ;-)

@gdha
I like to merge it today afternoon if you do not object.