Explain how to invoke GNU Make for parallel builds.

nt/INSTALL

@@ -43,7 +43,18 @@
        gmake
 
      (If you are building from CVS, say "make bootstrap" or "nmake
-     bootstrap" instead and avoid using Cygwin make.)
+     bootstrap" instead, and avoid using Cygwin make.)
+
+     With GNU Make, you can use the -j command-line option to have
+     Make execute several commands at once, like this:
+
+       gmake -j 4 XMFLAGS="-j 3"
+
+     The XMFLAGS variable overrides the default behavior of GNU Make
+     on Windows, whereby recursive Make invocations reset the maximum
+     number of simultaneous commands to 1.  The above command allows
+     up to 4 simultaneous commands at once in the top-level Make, and
+     up to 3 in each one of the recursive Make's.
 
   4. Generate the Info manuals (only if you are building out of CVS, and
      if you have makeinfo.exe installed):
@@ -252,6 +263,18 @@
   The warnings may be fixed in the main FSF source at some point, but
   until then we will just live with them.
 
+  With GNU Make, you can use the -j command-line option to have Make
+  execute several commands at once, like this:
+
+    gmake -j 4 XMFLAGS="-j 3"
+
+  The XMFLAGS variable overrides the default behavior of GNU Make on
+  Windows, whereby recursive Make invocations reset the maximum number
+  of simultaneous commands to 1.  The above command allows up to 4
+  simultaneous commands at once in the top-level Make, and up to 3 in
+  each one of the recursive Make's; you can use other numbers of jobs,
+  if you wish.
+
   If you are building from CVS, the following commands will produce
   the Info manuals (which are not part of the CVS repository):