Add WINDIRSDIR variable

rtl/inc/Makefile.rtl

@@ -1434,7 +1434,7 @@ WinApi.Windows$(PPUEXT): $(NSOSDIR)/WinApi.Windows.pp $(WINDOWS_DEPS)
 #
 # Windirs
 #
-WINDIRS_DEPS=windirs.pp $(WINDOWSUNIT)$(PPUEXT) $(SYSTEMUNIT)$(PPUEXT) \
+WINDIRS_DEPS=$(WINDIRSDIR)/windirs.pp $(WINDOWSUNIT)$(PPUEXT) $(SYSTEMUNIT)$(PPUEXT) \
              $(WINDIRS_DEPS_OS) $(WINDIRS_DEPS_CPU)
 
 windirs$(PPUEXT): $(WINDIRS_DEPS)

rtl/win32/Makefile.fpc

@@ -60,10 +60,11 @@ DLLS=fpcmemdll
 CPU_UNITS=$(CPUUNIT) $(SIGNALSUNIT) $(MMXUNIT)
 # Paths
 OBJPASDIR=$(RTL)/objpas
-FPC_SYSTEM_OPT=-Fu../win
+FPC_SYSTEM_OPT=-Fu$(WINDIR)
 SYSUTILSDIR=$(WINDIR)
-SYSUTILS_OPT=-Fi../win
+SYSUTILS_OPT=-Fi$(WINDIR)
 SYSUTILS_DEPS_OS=$(WINDOWSUNIT)$(PPUEXT) $(WINDIRSUNIT)$(PPUEXT)
+WINDIRSDIR=$(WINDIR)
 
 # Files used by windows.pp
 include $(WININC)/makefile.inc

rtl/win64/Makefile.fpc

@@ -58,6 +58,7 @@ NSOSDIR=$(NSDIR)/windows
 SYSUTILSDIR=$(WINDIR)
 SYSUTILS_OPT=-Fi../win
 SYSUTILS_DEPS_OS=$(WINDOWSUNIT)$(PPUEXT) $(WINDIRSUNIT)$(PPUEXT)
+WINDIRSDIR=$(WINDIR)
 
 UNITPREFIX=rtl
 SYSTEMUNIT=system