document MULTILIB_OSDIRNAMES, copied from genmultilib.
Ok for the trunk?
Matthias
PR bootstrap/25508
* doc/fragments.texi: Document MULTILIB_OSDIRNAMES.
Index: gcc/doc/fragments.texi
===================================================================
--- gcc/doc/fragments.texi (revision 177846)
+++ gcc/doc/fragments.texi (working copy)
@@ -128,6 +128,19 @@
of options to be used for all builds. If you set this, you should
probably set @code{CRTSTUFF_T_CFLAGS} to a dash followed by it.
+@findex MULTILIB_OSDIRNAMES
+@item MULTILIB_OSDIRNAMES
+If @code{MULTILIB_OPTIONS} is used, this variable specifies the list
+of OS subdirectory names. The format is either the same as of
+@code{MULTILIB_DIRNAMES}, or a set of mappings. When it is the same
+as @code{MULTILIB_DIRNAMES}, it describes the multilib directories
+using OS conventions, rather than GCC conventions. When it is a set
+of mappings of the form @code{gccdir=osdir}, the left side gives the
+GCC convention and the right gives the equivalent OS defined location.
+If the osdir part begins with a !, the os directory names are used
+exclusively. Use the mapping when there is no one-to-one equivalence
+between GCC levels and the OS.
+
@findex NATIVE_SYSTEM_HEADER_DIR
@item NATIVE_SYSTEM_HEADER_DIR
If the default location for system headers is not @file{/usr/include},
