update wasi-libc and Makefile to fix `<fstream>` (#375)

As of LLVM 17, which includes https://reviews.llvm.org/D152168, libcxx has
combined the old `_LIBCPP_HAS_NO_FILESYSTEM_LIBRARY` and
`_LIBCPP_HAS_NO_FSTREAM` preprocessor symbols into a single
`_LIBCPP_HAS_NO_FILESYSTEM` symbol, which means there's no longer any way to
enable `<fstream>` without enabling `<filesystem>`.

The solution is to set `-DLIBCXX_ENABLE_FILESYSTEM:BOOL=ON` and update
`wasi-libc`, which includes stubs for the functions required by libcxx's
`<filesystem>` implementation.

Fixes #373

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

Makefile

@@ -182,7 +182,7 @@ LIBCXX_CMAKE_FLAGS = \
     -DLIBCXX_ENABLE_SHARED:BOOL=$(2) \
     -DLIBCXX_ENABLE_EXPERIMENTAL_LIBRARY:BOOL=OFF \
     -DLIBCXX_ENABLE_EXCEPTIONS:BOOL=OFF \
-    -DLIBCXX_ENABLE_FILESYSTEM:BOOL=OFF \
+    -DLIBCXX_ENABLE_FILESYSTEM:BOOL=ON \
     -DLIBCXX_ENABLE_ABI_LINKER_SCRIPT:BOOL=OFF \
     -DLIBCXX_CXX_ABI=libcxxabi \
     -DLIBCXX_CXX_ABI_INCLUDE_PATHS=$(LLVM_PROJ_DIR)/libcxxabi/include \

src/wasi-libc

@@ -1 +1 @@
-Subproject commit 925ad6d75899397d26b9f09a6f195dbf5eb35814
+Subproject commit cc62fa82c29bfced82d280cbccc231667ee80822