Win32: keep --with-opt-dir as-is unless it is a real path

Allow to expand environment variables in Makefile.

E.g.:
```batch
set VCPKG_INSTALLED=%HOME%\vcpkg\vcpkg_installed
win32\configure.bat "--with-opt-dir=$(VCPKG_INSTALLED)/$(MACHINE)-windows"
```

1 files changed, 7 insertions, 5 deletions

diff --git a/win32/configure.bat b/win32/configure.bat
index 72c2a0139b..68ce7fb53f 100755
--- a/win32/configure.bat
+++ b/win32/configure.bat
@@ -5,12 +5,12 @@ set PROMPT=$E[94m+$E[m$S
 if "%~dp0" == "%CD%\" (

     echo don't run in win32 directory.

     exit /b 999

-) else if "%~0" == "%~nx0" (
+) else if "%~0" == "%~nx0" (

     set "WIN32DIR=%~$PATH:0"

-) else if "%~0" == "%~n0" (
+) else if "%~0" == "%~n0" (

     set "WIN32DIR=%~$PATH:0"

 ) else (

-    set "WIN32DIR=%~0"
+    set "WIN32DIR=%~0"

 )

 

 set "WIN32DIR=%WIN32DIR:\=/%:/:"

@@ -204,9 +204,11 @@ goto :loop ;
   )

   :optdir-loop

   for /f "delims=; tokens=1,*" %%I in ("%arg%") do (set "d=%%I" & set "arg=%%J")

-    pushd %d:/=\% && (

+    pushd %d:/=\% 2> nul && (

       set "optdirs=%optdirs%;%CD:\=/%"

       popd

+    ) || (

+      set "optdirs=%optdirs%;%d:\=/%"

     )

   if not "%arg%" == "" goto :optdir-loop

 goto :loop ;

@@ -239,7 +241,7 @@ goto :EOF
   exit /b 1

 :end

 if "%debug_configure%" == "yes" (type %confargs%)

-if not "%optdirs%" == "" (echo>>%config_make% optdirs = %optdirs:~1%)

+if defined optdirs (for %%I in ("%optdirs:~1%") do echo>>%config_make% optdirs = %%~I)

 (

   echo.

   echo configure_args = \