[contrib] Fix rom-o-matic git version number issues

Fixes issue in which git version number is not displayed on startup
when iPXE is built through rom-o-matic.

Remove special characters from filename generated by rom-o-matic (so
that you get "ipxe-1.0.0+c3b4-undionly.kkpxe" instead of
"ipxe-1.0.0+ (c3b4)-undionly.kkpxe")

Signed-off-by: Michael Brown <mcb30@ipxe.org>

contrib/rom-o-matic/build.php

 
 // Make the requested image.  $status is set to 0 on success
 $make_target = "bin/${nic}.${fmt_extension}";
-$make_cmd = "make -C '$build_dir' '$make_target' $emb_script_cmd 2>&1";
+$gitversion = exec('git describe --always --abbrev=1 --match "" 2>/dev/null');
+if ($gitversion) {
+	$gitversion = "GITVERSION=$gitversion";
+}
+
+$make_cmd = "make -C '$build_dir' '$make_target' $gitversion $emb_script_cmd 2>&1";
 
 exec ( $make_cmd, $maketxt, $status );
 
             // Delete build directory as soon as it is not needed
             rm_build_dir ();
 
-            $output_filename = "ipxe-${version}-${nic}.${fmt_extension}";
+            $output_filename = preg_replace('/[^a-z0-9\+\.\-]/i', '', "ipxe-${version}-${nic}.${fmt_extension}");
 
             // Try to force IE to handle downloading right.
             Header ( "Cache-control: private");