Fix clang compiler detection on Windows

A previous commit[1] left a "debug" statement, which causes clang
builds on Windows to fail always.

[1] <b3d6414b87>

Closes GH-17450.

NEWS

@@ -59,6 +59,9 @@ PHP                                                                        NEWS
   . Fixed bug GH-15833 (Segmentation fault (access null pointer) in
     ext/spl/spl_array.c). (nielsdos)
 
+- Windows:
+  . Fixed clang compiler detection. (cmb)
+
 - Zip:
   . Fixed bug GH-17139 (Fix zip_entry_name() crash on invalid entry).
     (nielsdos)

win32/build/confutils.js

@@ -3125,7 +3125,7 @@ function toolset_get_compiler_name(short)
 		var command = 'cmd /c ""' + PHP_CL + '" -v"';
 		var full = execute(command + '" 2>&1"');
 
-		ERROR(full.split(/\n/)[0].replace(/\s/g, ' '));
+		return full.split(/\n/)[0].replace(/\s/g, ' ');
 	}
 
 	WARNING("Unsupported toolset");