[libcxx][doc] Update the build documentation.
These are the hunks of
D106770 [libc++][doc] Update the release notes
that are relevant for main.
NOKEYCHECK=True
GitOrigin-RevId: 92b758cf3d706b117d59490cd85d23b764cc749f
diff --git a/docs/BuildingLibcxx.rst b/docs/BuildingLibcxx.rst
index 399f00b..a29a05b 100644
--- a/docs/BuildingLibcxx.rst
+++ b/docs/BuildingLibcxx.rst
@@ -246,10 +246,10 @@
.. option:: LIBCXX_ENABLE_FILESYSTEM:BOOL
- **Default**: ``ON`` except on Windows.
+ **Default**: ``ON`` except on Windows when using MSVC.
This option can be used to enable or disable the filesystem components on
- platforms that may not support them. For example on Windows.
+ platforms that may not support them. For example on Windows when using MSVC.
.. option:: LIBCXX_ENABLE_INCOMPLETE_FEATURES:BOOL