8007993: hotspot.log w/ enabled LogCompilation can be an invalid XML

Summary: Open compilation log files in write-mode and close before deletion attempt.
Reviewed-by: vlivanov

src/share/vm/compiler/compileBroker.cpp

@@ -1845,7 +1845,7 @@ void CompileBroker::init_compiler_thread_log() {
                      os::file_separator(), thread_id, os::current_process_id());
       }
 
-      fp = fopen(file_name, "at");
+      fp = fopen(file_name, "wt");
       if (fp != NULL) {
         if (LogCompilation && Verbose) {
           tty->print_cr("Opening compilation log %s", file_name);

src/share/vm/compiler/compileLog.cpp

@@ -55,8 +55,10 @@ CompileLog::CompileLog(const char* file_name, FILE* fp, intx thread_id)
 }
 
 CompileLog::~CompileLog() {
-  delete _out;
+  delete _out; // Close fd in fileStream::~fileStream()
   _out = NULL;
+  // Remove partial file after merging in CompileLog::finish_log_on_error
+  unlink(_file);
   FREE_C_HEAP_ARRAY(char, _identities, mtCompiler);
   FREE_C_HEAP_ARRAY(char, _file, mtCompiler);
 }
@@ -268,10 +270,9 @@ void CompileLog::finish_log_on_error(outputStream* file, char* buf, int buflen)
       }
       file->print_raw_cr("</compilation_log>");
       close(partial_fd);
-      unlink(partial_file);
     }
     CompileLog* next_log = log->_next;
-    delete log;
+    delete log; // Removes partial file
     log = next_log;
   }
   _first = NULL;