Help compiling image for Thinkpad T60

I'm following the instructions of the Build HOWTO section of the Coreboot Wiki (https://www.coreboot.org/Build_HOWTO) and I'm having some
issues.

Following the quote from the wiki "It is worth checking the Supported Motherboards (https://coreboot.org/status/board-status.html) page to see if
your mainboard is known to work with a particular version of coreboot. If your board is listed and
you want to try a known-working version, click the "upstream tree" link to find the commit hash and
then check it out in git:"

So I find the commit hash and run:

git checkout 87e36c442e33388493f259bfa14db460a4f02753

Which returns the output:

warning: unable to rmdir '3rdparty/intel-sec-tools': Directory not empty
warning: unable to rmdir '3rdparty/qc_blobs': Directory not empty
warning: unable to rmdir '3rdparty/stm': Directory not empty
Updating files: 100% (8604/8604), done.
M 3rdparty/amd_blobs
M 3rdparty/arm-trusted-firmware
M 3rdparty/blobs
M 3rdparty/chromeec
M 3rdparty/fsp
M 3rdparty/intel-microcode
M 3rdparty/libgfxinit
M 3rdparty/libhwbase
M 3rdparty/vboot
Note: switching to '87e36c442e33388493f259bfa14db460a4f02753'.

You are in 'detached HEAD' state. You can look around, make experimental
changes and commit them, and you can discard any commits you make in this
state without impacting any branches by switching back to a branch.

If you want to create a new branch to retain commits you create, you may
do so (now or later) by using -c with the switch command. Example:

git switch -c <new-branch-name>

Or undo this operation with:

git switch -

Turn off this advice by setting config variable advice.detachedHead to false

If I try to proceed with:

git submodule update --checkout

I receive the output:

fatal: remote error: upload-pack: not our ref 0ac1af437d2cc461b94bd2cdaa195e86dd481d37
Fetched in submodule path '3rdparty/amd_blobs', but it did not contain 0ac1af437d2cc461b94bd2cdaa195e86dd481d37. Direct fetching of that commit failed.

I'm not that familiar with git so I apologize if this is a simple problem. Sorry for the spam too, I missclicked the return key.