winbuild: Document the option used to statically link the CRT

- Document option RTLIBCFG (runtime library configuration).

Bug: https://github.com/bagder/curl/issues/254
Reported-by: Bert Huijben

diff --git a/winbuild/BUILD.WINDOWS.txt b/winbuild/BUILD.WINDOWS.txt
index 7d6b364e24d88e3bf394234ab34485b6b9cc5137..600f7374699a122d4f1ce73bf4c1892ca3cce749 100644 (file)
--- a/winbuild/BUILD.WINDOWS.txt
+++ b/winbuild/BUILD.WINDOWS.txt
@@ -76,3 +76,14 @@ where <options> is one or many of:
   GEN_PDB=<yes or no>          - Generate Program Database (debug symbols for release build)\r
   DEBUG=<yes or no>            - Debug builds\r
   MACHINE=<x86 or x64>         - Target architecture (default is x86)\r
+\r
+Static linking of Microsoft's C RunTime (CRT):\r
+==============================================\r
+If you are using mode=static nmake will create and link to the static build of\r
+libcurl but *not* the static CRT. If you must you can force nmake to link in\r
+the static CRT by passing RTLIBCFG=static. Typically you shouldn't use that\r
+option, and nmake will default to the DLL CRT. RTLIBCFG is rarely used and\r
+therefore rarely tested. When passing RTLIBCFG for a configuration that was\r
+already built but not with that option, or if the option was specified\r
+differently, you must destroy the build directory containing the configuration\r
+so that nmake can build it from scratch.\r