Tell coreconf where the nspr header files are in the mozilla client

build.

security/nss/makefile.win

@@ -43,6 +43,7 @@ include <$(DEPTH)\config\config.mak>
 GMAKE = gmake.exe
 
 GMAKE_FLAGS = OBJDIR_NAME=$(OBJDIR) MOZILLA_CLIENT=1
+GMAKE_FLAGS = $(GMAKE_FLAGS) SOURCE_MDHEADERS_DIR=$(MOZ_SRC:\=/)/mozilla/dist/include/nspr
 
 #
 # The Client's debug build uses MSVC's debug runtime library (/MDd).