LIBPATHENV on Windows

* configure.in, win32/Makefile.sub: set LIBPATHENV to PATH on
  Windows, for extra DLLs.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59868 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

configure.in

@@ -3446,7 +3446,7 @@ AS_IF([test "$with_dln_a_out" != yes], [
 			: ${LDSHARED='$(CC) -shared'}
 			XLDFLAGS="$XLDFLAGS -Wl,--stack,0x00200000,--enable-auto-import"
 			DLDFLAGS="${DLDFLAGS} -Wl,--enable-auto-image-base,--enable-auto-import"
-			: ${LIBPATHENV=""}
+			: ${LIBPATHENV=PATH}
 			: ${PRELOADENV=""}
 			rb_cv_dlopen=yes],
 	[hiuxmpp], [	: ${LDSHARED='$(LD) -r'}],

win32/Makefile.sub

@@ -917,6 +917,8 @@ s,@OUTFLAG@,$(OUTFLAG),;t t
 s,@COUTFLAG@,$(COUTFLAG),;t t
 s,@CSRCFLAG@,$(CSRCFLAG),;t t
 s,@CPPOUTFILE@,-P,;t t
+s,@PRELOADENV@,,;t t
+s,@LIBPATHENV@,PATH,;t t
 s,@LIBPATHFLAG@, -libpath:%s,;t t
 s,@RPATHFLAG@,,;t t
 s,@LIBARG@,%s.lib,;t t