base-nova: Synchronize output to serial console with the hypervisor.

repos/base/src/core/core_log.cc

@@ -45,8 +45,10 @@ void Genode::init_core_log(Core_log_range const &r) { range = r; }
 
 void Genode::Core_log::output(char const * str)
 {
+	acquire();
 	for (unsigned i = 0; i < Genode::strlen(str); i++) {
 		out(str[i]);
 		out_mem(str[i]);
 	}
+	release();
 }

repos/base/src/core/include/core_log.h

@@ -31,6 +31,10 @@ namespace Genode {
 
 struct Genode::Core_log
 {
+	void acquire();
+
+	void release();
+
 	void out(char const c);
 
 	void output(char const * str);