Install libc++ module definitions

build-libcxx.sh

@@ -103,6 +103,7 @@ for arch in $ARCHS; do
         -DLIBCXX_CXX_ABI=libcxxabi \
         -DLIBCXX_LIBDIR_SUFFIX="" \
         -DLIBCXX_INCLUDE_TESTS=FALSE \
+        -DLIBCXX_INSTALL_MODULES=ON \
         -DLIBCXX_ENABLE_ABI_LINKER_SCRIPT=FALSE \
         -DLIBCXXABI_USE_COMPILER_RT=ON \
         -DLIBCXXABI_USE_LLVM_UNWINDER=ON \