doc: upmerge fixes

- Upgrade to latest Sphinx
- Fix some references
- Fix Zephyr docset required env vars

Signed-off-by: Gerard Marull-Paretas <[email protected]>

Author: gmarull

Diff for: doc/nrf/releases_and_maturity/releases/release-notes-1.4.1.rst

@@ -92,7 +92,7 @@ Zephyr changes incorporated into |NCS|
 
 This section contains changes in Zephyr that were cherry-picked into |NCS| for this release.
 
-* Added support for the :ref:`zephyr:actinius_icarus` board.
+* Added support for the :zephyr:board:`actinius_icarus` board.
 
 Bluetooth Host
 ~~~~~~~~~~~~~~

Diff for: doc/requirements.txt

@@ -14,7 +14,7 @@ PyYAML                          # |  X  |         |        |         |         |
 pykwalify                       # |     |         |        |         |         |      |   X    |
 pytest                          # |     |         |        |         |         |      |   X    |
 recommonmark                    # |     |         |   X    |    X    |         |      |        |
-sphinx~=7.4                     # |  X  |    X    |   X    |    X    |    X    |  X   |   X    |
+sphinx~=8.1                     # |  X  |    X    |   X    |    X    |    X    |  X   |   X    |
 sphinx-autobuild                # |  X  |    X    |   X    |    X    |    X    |  X   |   X    |
 sphinx-copybutton               # |  X  |         |        |         |         |      |   X    |
 sphinx-ncs-theme<1.1            # |  X  |         |        |         |         |      |        |

Diff for: doc/zephyr/conf.py

@@ -27,7 +27,7 @@
 
 # Import all Zephyr configuration, override as needed later
 os.environ["ZEPHYR_BASE"] = str(ZEPHYR_BASE)
-os.environ["ZEPHYR_BUILD"] = str(utils.get_builddir() / "zephyr")
+os.environ["OUTPUT_DIR"] = str(utils.get_builddir() / "html" / "zephyr")
 
 conf = eval_config_file(str(ZEPHYR_BASE / "doc" / "conf.py"), tags)
 locals().update(conf)