Fix the handling of --with-zlib-include

The handling was Unix centric, already in Configure.  Change that to
just collect the value and let the build file templates figure out
what to do with it.
Reviewed-by: NMatt Caswell <matt@openssl.org>

Configurations/descrip.mms.tmpl

@@ -468,13 +468,20 @@ EOF
       my $incs_on = "\@ !";
       my $incs_off = "\@ !";
       my $incs = "";
-      if (@{$args{incs}}) {
+      my @incs = ();
+      push @incs, @{$args{incs}} if @{$args{incs}};
+      unless ($disabled{zlib}) {
+          # GNV$ZLIB_INCLUDE is the standard logical name for later zlib
+          # incarnations.
+          push @incs, ($withargs{zlib_include} || 'GNV$ZLIB_INCLUDE:');
+      }
+      if (@incs) {
           $incs_on =
               "DEFINE tmp_includes "
               .join(",-\n\t\t\t", map {
                                       file_name_is_absolute($_)
                                       ? $_ : catdir($backward,$_)
-                                  } @{$args{incs}});
+                                  } @incs);
           $incs_off = "DEASSIGN tmp_includes";
           $incs = " /INCLUDE=(tmp_includes:)";
       }

Configurations/unix-Makefile.tmpl

@@ -860,6 +860,11 @@ EOF
       my $srcs = join(" ",  @srcs);
       my $deps = join(" ", @srcs, @{$args{deps}});
       my $incs = join("", map { " -I".$_ } @{$args{incs}});
+      unless ($disabled{zlib}) {
+          if ($withargs{zlib_include}) {
+              $incs .= " -I".$withargs{zlib_include};
+          }
+      }
       my $ecflags = { lib => '$(LIB_CFLAGS)',
                       dso => '$(DSO_CFLAGS)',
                       bin => '$(BIN_CFLAGS)' } -> {$args{intent}};

Configurations/windows-makefile.tmpl

@@ -300,6 +300,11 @@ EOF
      my $srcs = join(" ",  @srcs);
      my $deps = join(" ", @srcs, @{$args{deps}});
      my $incs = join("", map { " /I ".$_ } @{$args{incs}});
+     unless ($disabled{zlib}) {
+         if ($withargs{zlib_include}) {
+             $incs .= " /I ".$withargs{zlib_include};
+         }
+     }
      my $ecflags = { lib => '$(LIB_CFLAGS)',
 		     dso => '$(DSO_CFLAGS)',
 		     bin => '$(BIN_CFLAGS)' } -> {$args{intent}};

Configure

@@ -672,7 +672,7 @@ foreach (@argvcopy)
 			}
 		elsif (/^--with-zlib-include=(.*)$/)
 			{
-			$withargs{zlib_include}="-I$1";
+			$withargs{zlib_include}=$1;
 			}
 		elsif (/^--with-fipslibdir=(.*)$/)
 			{