tools/docs: sphinx-build-wrapper: generate rust docs only once

Currently the rust docs are generated for each entry in SPHINXDIRS.
This is unnecessary as they will be the same for each one.

Move the generation, so it is executed only once.

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-v1-1-998e14b9ed9e@weissschuh.net>

Author: t-8ch

tools/docs/sphinx-build-wrapper

@@ -352,23 +352,6 @@ class SphinxBuilder:
             except (OSError, IOError) as e:
                 print(f"Warning: Failed to copy CSS: {e}", file=sys.stderr)
 
-        if self.rustdoc:
-            print("Building rust docs")
-            if "MAKE" in self.env:
-                cmd = [self.env["MAKE"]]
-            else:
-                cmd = ["make", "LLVM=1"]
-
-            cmd += [ "rustdoc"]
-            if self.verbose:
-                print(" ".join(cmd))
-
-            try:
-                subprocess.run(cmd, check=True)
-            except subprocess.CalledProcessError as e:
-                print(f"Ignored errors when building rustdoc: {e}. Is RUST enabled?",
-                      file=sys.stderr)
-
     def build_pdf_file(self, latex_cmd, from_dir, path):
         """Builds a single pdf file using latex_cmd"""
         try:
@@ -785,6 +768,23 @@ class SphinxBuilder:
         elif target == "infodocs":
             self.handle_info(output_dirs)
 
+        if self.rustdoc and target in ["htmldocs", "epubdocs"]:
+            print("Building rust docs")
+            if "MAKE" in self.env:
+                cmd = [self.env["MAKE"]]
+            else:
+                cmd = ["make", "LLVM=1"]
+
+            cmd += [ "rustdoc"]
+            if self.verbose:
+                print(" ".join(cmd))
+
+            try:
+                subprocess.run(cmd, check=True)
+            except subprocess.CalledProcessError as e:
+                print(f"Ignored errors when building rustdoc: {e}. Is RUST enabled?",
+                      file=sys.stderr)
+
 def jobs_type(value):
     """
     Handle valid values for -j. Accepts Sphinx "-jauto", plus a number