external/clucene: Avoid ASan wcsncpy-param-overlap

...as seen after
<https://github.com/llvm/llvm-project/commit/6ca835b7f4349ad55c8e8afdf0669927b6b284b4>
"[compiler-rt][asan] Add wcscpy/wcsncpy; enable wcscat/wcsncat on Windows
(#160493)" when building Extension_nlpsolver,

> ==1084736==ERROR: AddressSanitizer: wcsncpy-param-overlap: memory ranges [0x7cacc15e1480,0x7cacc15e1498) and [0x7cacc15e1480, 0x7cacc15e1498) overlap
>  #0 in wcsncpy at ~/github.com/llvm/llvm-project/compiler-rt/lib/asan/asan_interceptors.cpp:664:5
>  #1 in lucene::util::StringBuffer::prepend(wchar_t const*, unsigned long) at workdir/UnpackedTarball/clucene/src/shared/CLucene/util/StringBuffer.cpp:233:7
>  #2 in lucene::util::StringBuffer::prepend(wchar_t const*) at workdir/UnpackedTarball/clucene/src/shared/CLucene/util/StringBuffer.cpp:214:7
>  #3 in lucene::analysis::standard::StandardTokenizer::ReadNumber(wchar_t const*, wchar_t, lucene::analysis::Token*) at workdir/UnpackedTarball/clucene/src/core/CLucene/analysis/standard/StandardTokenizer.cpp:181:11
>  #4 in lucene::analysis::standard::StandardTokenizer::ReadNumber(wchar_t const*, wchar_t, lucene::analysis::Token*) at workdir/UnpackedTarball/clucene/src/core/CLucene/analysis/standard/StandardTokenizer.cpp:238:16
>  #5 in lucene::analysis::standard::StandardTokenizer::next(lucene::analysis::Token*) at workdir/UnpackedTarball/clucene/src/core/CLucene/analysis/standard/StandardTokenizer.cpp:160:13
>  #6 in lucene::analysis::standard::StandardFilter::next(lucene::analysis::Token*) at workdir/UnpackedTarball/clucene/src/core/CLucene/analysis/standard/StandardFilter.cpp:27:16
>  #7 in lucene::analysis::LowerCaseFilter::next(lucene::analysis::Token*) at workdir/UnpackedTarball/clucene/src/core/CLucene/analysis/Analyzers.cpp:151:13
>  #8 in lucene::analysis::StopFilter::next(lucene::analysis::Token*) at workdir/UnpackedTarball/clucene/src/core/CLucene/analysis/Analyzers.cpp:218:16
>  #9 in lucene::index::DocumentsWriter::ThreadState::FieldData::invertField(lucene::document::Field*, lucene::analysis::Analyzer*, int) at workdir/UnpackedTarball/clucene/src/core/CLucene/index/DocumentsWriterThreadState.cpp:901:32
>  #10 in lucene::index::DocumentsWriter::ThreadState::FieldData::processField(lucene::analysis::Analyzer*) at workdir/UnpackedTarball/clucene/src/core/CLucene/index/DocumentsWriterThreadState.cpp:798:9
>  #11 in lucene::index::DocumentsWriter::ThreadState::processDocument(lucene::analysis::Analyzer*) at workdir/UnpackedTarball/clucene/src/core/CLucene/index/DocumentsWriterThreadState.cpp:557:24
>  #12 in lucene::index::DocumentsWriter::updateDocument(lucene::document::Document*, lucene::analysis::Analyzer*, lucene::index::Term*) at workdir/UnpackedTarball/clucene/src/core/CLucene/index/DocumentsWriter.cpp:946:16
>  #13 in lucene::index::DocumentsWriter::addDocument(lucene::document::Document*, lucene::analysis::Analyzer*) at workdir/UnpackedTarball/clucene/src/core/CLucene/index/DocumentsWriter.cpp:930:10
>  #14 in lucene::index::IndexWriter::addDocument(lucene::document::Document*, lucene::analysis::Analyzer*) at workdir/UnpackedTarball/clucene/src/core/CLucene/index/IndexWriter.cpp:685:28
>  #15 in HelpIndexer::indexDocuments() at helpcompiler/source/HelpIndexer.cxx:125:21
>  #16 in main at helpcompiler/source/HelpIndexer_main.cxx:79:22
>
> 0x7cacc15e1480 is located 0 bytes inside of 1024-byte region [0x7cacc15e1480,0x7cacc15e1880)
> allocated by thread T0 here:
>  #0 in malloc at ~/github.com/llvm/llvm-project/compiler-rt/lib/asan/asan_malloc_linux.cpp:67:3
>  #1 in lucene::analysis::Token::growBuffer(unsigned long) at workdir/UnpackedTarball/clucene/src/core/CLucene/analysis/AnalysisHeader.cpp:162:21
>  #2 in lucene::analysis::standard::StandardTokenizer::ReadAlphaNum(wchar_t, lucene::analysis::Token*) at workdir/UnpackedTarball/clucene/src/core/CLucene/analysis/standard/StandardTokenizer.cpp:260:8
>  #3 in lucene::analysis::standard::StandardTokenizer::next(lucene::analysis::Token*) at workdir/UnpackedTarball/clucene/src/core/CLucene/analysis/standard/StandardTokenizer.cpp:154:13
>  #4 in lucene::analysis::standard::StandardFilter::next(lucene::analysis::Token*) at workdir/UnpackedTarball/clucene/src/core/CLucene/analysis/standard/StandardFilter.cpp:27:16
>
> SUMMARY: AddressSanitizer: wcsncpy-param-overlap workdir/UnpackedTarball/clucene/src/shared/CLucene/util/StringBuffer.cpp:233:7 in lucene::util::StringBuffer::prepend(wchar_t const*, unsigned long)
> ==1084736==ABORTING
> make[1]: *** [nlpsolver/Extension_nlpsolver.mk:14: workdir/Extension/nlpsolver/root/help/de.done] Error 1

That wcsncpy move of a memory range onto itself looks a bit scary, but appears
to be by design of how recursive invocations of StandardTokenizer::ReadNumber
work.

Change-Id: I3ce9cc8343140ee287fac7db46b28e5adb7b67f9
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/192069
Reviewed-by: Stephan Bergmann <stephan.bergmann@collabora.com>
Tested-by: Jenkins

external/clucene/UnpackedTarball_clucene.mk

@@ -57,6 +57,7 @@ $(eval $(call gb_UnpackedTarball_add_patches,clucene,\
 	external/clucene/patches/enumarith.patch \
 	external/clucene/patches/clucene-reprobuild.patch.1 \
 	external/clucene/patches/clucene-const.patch.1 \
+	external/clucene/patches/wcsncpy.patch \
 ))
 
 ifneq ($(OS),WNT)

external/clucene/patches/wcsncpy.patch

@@ -0,0 +1,11 @@
+--- src/shared/CLucene/util/StringBuffer.cpp
++++ src/shared/CLucene/util/StringBuffer.cpp
+@@ -230,7 +230,7 @@
+ 	  }
+ 
+       //Copy the string value into the buffer at postion 0
+-      _tcsncpy(buffer, value, prependedLength);
++      if (value != buffer) _tcsncpy(buffer, value, prependedLength);
+       //Add the length of the copied string to len to reflect the new length of the string in
+       //the buffer (Note: len is not the bufferlength!)
+       len += prependedLength;