8009062: poor performance of JNI AttachCurrentThread after fix for 7017193

Don't re-evaluate stack bounds for main thread before install guard page

Reviewed-by: coleenp, dholmes, dlong

hotspot/src/share/vm/runtime/os.hpp

@@ -725,10 +725,6 @@ class os: AllStatic {
   // Hook for os specific jvm options that we don't want to abort on seeing
   static bool obsolete_option(const JavaVMOption *option);
 
-  // Read file line by line. If line is longer than bsize,
-  // rest of line is skipped. Returns number of bytes read or -1 on EOF
-  static int get_line_chars(int fd, char *buf, const size_t bsize);
-
   // Extensions
 #include "runtime/os_ext.hpp"