If NSPR20 isn't defined, the makefile wouldn't look in the NSPR header directory.

cmd/winfe/xpstrdll/src/makefile.win

@@ -1,84 +0,0 @@
-IGNORE_MANIFEST=1
-# The contents of this file are subject to the Netscape Public License
-# Version 1.0 (the "NPL"); you may not use this file except in
-# compliance with the NPL.  You may obtain a copy of the NPL at
-# http://www.mozilla.org/NPL/
-#
-# Software distributed under the NPL is distributed on an "AS IS" basis,
-# WITHOUT WARRANTY OF ANY KIND, either express or implied. See the NPL
-# for the specific language governing rights and limitations under the
-# NPL.
-#
-# The Initial Developer of this code under the NPL is Netscape
-# Communications Corporation.  Portions created by Netscape are
-# Copyright (C) 1998 Netscape Communications Corporation.  All Rights
-# Reserved.
-
-
-DLLNAME         = xpstrdll
-PDBFILE         = $(DLLNAME).pdb
-MAPFILE         = $(DLLNAME).map
-DLL             =.\$(OBJDIR)\$(DLLNAME).dll
-DEFFILE         = xpstrdll.def
-RESFILE         = xpstrdll.res
-MAKE_OBJ_TYPE   = DLL
-
-DEPTH=..\..\..\..
-
-OBJS = $(OBJS) .\$(OBJDIR)\xpstrdll.obj
-RCFLAGS=\
-	/I$(DEPTH)\include \
-	/I$(DIST)\include \
-	/I$(DEPTH)\dist\public\security \
-!if "$(MOZ_BITS)" == "32"
-	/DWIN32 \
-	/DXP_PC \
-	/Dx386 \
-	/D_X86_ \
-	/DLAYERS \
-	/DMQUOTE \
-	/D_MBCS \
-	/DJAVA_WIN32 \
-	/DHW_THREADS \
-	/DMSVC4 \
-!endif
-!if defined(MOZ_DEBUG)
-	/DDEBUG \
-!else
-	/DNODEBUG \
-!endif
-!if defined(MOZ_JAVA)
-	/DJAVA \
-!endif
-	/D_IMAGE_CONVERT
-
-MODULE=xpstrdll 
-DEPTH=..\..\..\.. 
-REQUIRES=coreincl nspr security 
-CPPSRCS=xpstrdll.cpp 
-CPP_OBJS=.\$(OBJDIR)\xpstrdll.obj 
-!if "$(MOZ_BITS)" != "16"
-LINCS=-I$(XPDIST)\public\coreincl -I$(XPDIST)\public\nspr \
-    -I$(XPDIST)\public\security 
-!endif
-!if "$(MOZ_BITS)"=="32" && defined(MOZ_DEBUG) && defined(GLOWCODE)
-LLIBS=$(LLIBS) $(GLOWDIR)\glowcode.lib
-!endif
-
-## Include support for MOZ_LITE/MOZ_MEDIUM
-include <$(DEPTH)/config/liteness.mak>
-
-# MOZ_LITENESS_FLAGS uses the -D options, not /D
-RCFLAGS=$(RCFLAGS) $(MOZ_LITENESS_FLAGS)
-
-!include "$(DEPTH)\config\rules.mak"
-
-.\$(OBJDIR)\xpstrdll.res : $(MOZ_SRC)\mozilla\include\allxpstr.rc
-
-$(DLL) : .\$(OBJDIR)\xpstrdll.res
-
-libs:: $(DLL)
-       $(MAKE_INSTALL) .\$(OBJDIR)\$(DLLNAME).dll $(DIST)\bin
-       $(MAKE_INSTALL) .\$(OBJDIR)\$(DLLNAME).lib $(DIST)\lib
-
-