tools/docs: sphinx-build-wrapper: compute sphinxdirs_list earlier

An upcoming patch will require sphinxdirs_list to be available before
the call to check_rust().

Move it up in the function.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Reviewed-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Tested-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <20260118-docs-spurious-rust-v1-3-998e14b9ed9e@weissschuh.net>

Author: t-8ch

tools/docs/sphinx-build-wrapper

@@ -670,6 +670,19 @@ class SphinxBuilder:
         if kerneldoc.startswith(self.srctree):
             kerneldoc = os.path.relpath(kerneldoc, self.srctree)
 
+        if not sphinxdirs:
+            sphinxdirs = os.environ.get("SPHINXDIRS", ".")
+
+        #
+        # sphinxdirs can be a list or a whitespace-separated string
+        #
+        sphinxdirs_list = []
+        for sphinxdir in sphinxdirs:
+            if isinstance(sphinxdir, list):
+                sphinxdirs_list += sphinxdir
+            else:
+                sphinxdirs_list += sphinxdir.split()
+
         args = [ "-b", builder, "-c", docs_dir ]
 
         if builder == "latex":
@@ -682,9 +695,6 @@ class SphinxBuilder:
         if rustdoc:
             args.extend(["-t", "rustdoc"])
 
-        if not sphinxdirs:
-            sphinxdirs = os.environ.get("SPHINXDIRS", ".")
-
         #
         # The sphinx-build tool has a bug: internally, it tries to set
         # locale with locale.setlocale(locale.LC_ALL, ''). This causes a
@@ -695,16 +705,6 @@ class SphinxBuilder:
         except locale.Error:
             self.env["LC_ALL"] = "C"
 
-        #
-        # sphinxdirs can be a list or a whitespace-separated string
-        #
-        sphinxdirs_list = []
-        for sphinxdir in sphinxdirs:
-            if isinstance(sphinxdir, list):
-                sphinxdirs_list += sphinxdir
-            else:
-                sphinxdirs_list += sphinxdir.split()
-
         #
         # Step 1:  Build each directory in separate.
         #