construct_lcp.cpp KEY_TEXT warning

[donpellegrino]

When compiling with the Intel oneAPI DPC++/C++ Compiler:

Intel(R) oneAPI DPC++/C++ Compiler 2022.0.0 (2022.0.0.20211123)
Target: x86_64-unknown-linux-gnu
Thread model: posix

The following warning is reported for construct_lcp.cpp:

[ 28%] Building CXX object lib/CMakeFiles/sdsl.dir/construct_lcp.cpp.o
cd /home/u133615/src/sdsl-lite/build/lib && /glob/development-tools/versions/oneapi/2022.1.2/oneapi/compiler/2022.0.2/linux/bin/icpx  -DMODE_TI -I/home/u133615/src/sdsl-lite/build/lib/../include -I/home/u133615/src/sdsl-lite/build/lib/../external/libdivsufsort/include -I/home/u133615/src/sdsl-lite/include  -std=c++11 -DNDEBUG -O3 -DNDEBUG   -o CMakeFiles/sdsl.dir/construct_lcp.cpp.o -c /home/u133615/src/sdsl-lite/lib/construct_lcp.cpp
In file included from /home/u133615/src/sdsl-lite/lib/construct_lcp.cpp:6:
/home/u133615/src/sdsl-lite/build/lib/../include/sdsl/construct_lcp.hpp:130:53: warning: instantiation of variable 'sdsl::key_text_trait<'\b'>::KEY_TEXT' required here, but no definition is available [-Wundefined-var-template]
    const char* KEY_TEXT = key_text_trait<t_width>::KEY_TEXT;
                                                    ^
/home/u133615/src/sdsl-lite/lib/construct_lcp.cpp:209:25: note: in instantiation of function template specialization 'sdsl::construct_lcp_PHI<(unsigned char)'\b'>' requested here
                        construct_lcp_PHI<8>(config);
                        ^
/home/u133615/src/sdsl-lite/build/lib/../include/sdsl/config.hpp:51:24: note: forward declaration of template entity is here
    static const char* KEY_TEXT;
                       ^
/home/u133615/src/sdsl-lite/build/lib/../include/sdsl/construct_lcp.hpp:130:53: note: add an explicit instantiation declaration to suppress this warning if 'sdsl::key_text_trait<'\b'>::KEY_TEXT' is explicitly instantiated in another translation unit
    const char* KEY_TEXT = key_text_trait<t_width>::KEY_TEXT;
                                                    ^
1 warning generated.