Toolkit v4 has header files with the same names as EMX ones...

--- ./Makefile.PL-pre	Tue Nov  4 13:57:26 2003
+++ ./Makefile.PL	Thu Dec  4 00:54:10 2003
@@ -41,8 +41,12 @@ if (!@tk) {
 if (@tk) {
     die "Multiple @tk arguments not allowed.\n" if @tk > 1;
     $tk[0] =~ /TOOLKIT=(.*)/;
-    $inc = "-I$1/h -I$1/som/include";
-    $lib = "-L$1/som/lib ";
+    my $d = $1;
+    # Must put standard directories first, otherwise toolkit C LIB headers
+    # get in the way:
+    my @emx = map "-I$_", split /;/, ($ENV{C_INCLUDE_PATH} || "");
+    $inc = "@emx -I$d/h -I$d/som/include";
+    $lib = "-L$d/som/lib ";
 }
 
 my @opt;