build-libcxx: Don't manually undefine _LIBCXXABI_DISABLE_VISIBILITY_ANNOTATIONS

Instead set the cmake defines that indicate that libcxx is going
to be linked dynamically and going to link in libcxxabi statically,
so that libcxxabi is built statically but with dllexport attributes.

build-libcxx.sh

@@ -174,11 +174,6 @@ build_all() {
         [ -z "$CLEAN" ] || rm -rf build-$arch-$type
         mkdir -p build-$arch-$type
         cd build-$arch-$type
-        if [ "$type" = "shared" ]; then
-            LIBCXXABI_VISIBILITY_FLAGS="-U_LIBCXXABI_DISABLE_VISIBILITY_ANNOTATIONS"
-        else
-            LIBCXXABI_VISIBILITY_FLAGS=""
-        fi
         cmake \
             ${CMAKE_GENERATOR+-G} "$CMAKE_GENERATOR" \
             -DCMAKE_BUILD_TYPE=Release \
@@ -202,7 +197,8 @@ build_all() {
             -DLIBCXXABI_LIBDIR_SUFFIX="" \
             -DLIBCXXABI_ENABLE_NEW_DELETE_DEFINITIONS=ON \
             -DCXX_SUPPORTS_CXX_STD=TRUE \
-            -DCMAKE_CXX_FLAGS="$LIBCXXABI_VISIBILITY_FLAGS" \
+            -DLIBCXX_ENABLE_SHARED=$SHARED \
+            -DLIBCXX_ENABLE_STATIC_ABI_LIBRARY=TRUE \
             ..
         $BUILDCMD ${CORES+-j$CORES}
         cd ..