Help CMake locate the "tools-extra" directory.

Taken from <https://bugs.llvm.org/show_bug.cgi?id=49990#c3>.

diff --git a/clang-tools-extra/clangd/quality/CompletionModel.cmake b/clang-tools-extra/clangd/quality/CompletionModel.cmake
--- a/clangd/quality/CompletionModel.cmake
+++ b/clangd/quality/CompletionModel.cmake
@@ -5,7 +5,7 @@
 # will define a C++ class called ${cpp_class} - which may be a
 # namespace-qualified class name.
 function(gen_decision_forest model filename cpp_class)
-  set(model_compiler ${CMAKE_SOURCE_DIR}/../clang-tools-extra/clangd/quality/CompletionModelCodegen.py)
+  set(model_compiler ${CMAKE_CURRENT_LIST_DIR}/quality/CompletionModelCodegen.py)
   
   set(output_dir ${CMAKE_CURRENT_BINARY_DIR})
   set(header_file ${output_dir}/${filename}.h)
ripts'>koszko-scripts</option>
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<div class='path'>path: <a href='/guix/log/?id=74b012310f22836db05cd63d9ac2d88c1d4b9efe'>root</a>/<a href='/guix/log/tests?id=74b012310f22836db05cd63d9ac2d88c1d4b9efe'>tests</a>/<a href='/guix/log/tests/cran.scm?id=74b012310f22836db05cd63d9ac2d88c1d4b9efe'>cran.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/tests/cran.scm?id=74b012310f22836db05cd63d9ac2d88c1d4b9efe&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2021-12-18 04:09:47 +0100'>2021-12-18</span></td><td><a href='/guix/commit/tests/cran.scm?id=10ceb3e84654e024f14a4b048e7d68492ed9dc7c'>import: cran: Fix description-&gt;package test.</a><span class='msg-avail'>...<span class='msg-tooltip'>This follows up on commit 5cd1019488c44081aaf030fbe8bc357d78daef23.

* tests/cran.scm (description): Include a very long line.
(description-&gt;package): Update the golden description to match the
paragraph filling now performed by BEAUTIFY-DESCRIPTION.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2021-07-11 00:49:16 +0200'>2021-07-11</span></td><td><a href='/guix/commit/tests/cran.scm?id=aa6921634b4ea9988af0e37bfbb56780c431ef64'>import: cran: Emit new-style package inputs.</a><span class='msg-avail'>...<span class='msg-tooltip'>* guix/import/cran.scm (format-inputs): Emit symbols or
'specification-&gt;package' calls.
(maybe-inputs): Wrap in 'list' instead of 'quasiquote'.
* tests/cran.scm ("description-&gt;package"): Adjust accordingly.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-01-16 23:14:05 +0100'>2020-01-16</span></td><td><a href='/guix/commit/tests/cran.scm?id=cfd1ed84013df85f0e473884ef4038b4bd7120d4'>import: cran: Avoid uses of '@@' in the tests.</a><span class='msg-avail'>...<span class='msg-tooltip'>* guix/import/cran.scm (description-&gt;alist, description-&gt;package): Export.
&lt;top level&gt;: Set! 'listify'.
* tests/cran.scm (description-alist, "description-&gt;package"): Remove use
of '@@' to access the relevant bindings.
</span></span></td><td>Ludovic Courtès</td></tr>