add build with libc++ script.

scripts/bootstrap-cmake-linux-libcpp.sh

@@ -0,0 +1,15 @@
+curdir=`pwd`
+
+builddir=${curdir}/build_libcpp
+
+rm -rf ${builddir}
+mkdir ${builddir}
+
+# with lld linker
+#  -DCMAKE_TOOLCHAIN_FILE=cmake/lld-linux.toolchain.cmake 
+
+cd ${builddir} && CXX=clang++-18 CC=clang-18 cmake \
+  -DCMAKE_CXX_FLAGS="-stdlib=libc++" \
+  -DCMAKE_VERBOSE_MAKEFILE=1 \
+  ..
+