Implement first intrinsics for output

tests/expectations/print_boolean.txt

@@ -1,2 +1,2 @@
-1
-0
+t
+f

tests/print_boolean.eln

@@ -1,4 +1,4 @@
 begin
-  ? True;
-  ? False
+  writeb(True);
+  writeb(False)
 end.

tests/subtraction.eln

@@ -1,2 +1,2 @@
-write(5 - 4)
+writei(5 - 4)
 .

tests/tester.cpp

@@ -114,9 +114,8 @@ namespace elna
 
         boost::asio::io_service io_service;
         std::future<std::string> buffer;
-        boost::process::child spike(
-            "/opt/riscv/bin/spike", "--isa=RV32IMAC",
-            "/opt/riscv/riscv32-unknown-elf/bin/pk",
+        boost::process::child qemu(
+            boost::process::search_path("qemu-riscv32"),
             test_binary.string(),
             boost::process::std_out > buffer,
             boost::process::std_err > buffer,
@@ -124,7 +123,7 @@ namespace elna
         );
         io_service.run();
 
-        return test_result{ test_status::successful, spike.exit_code(), buffer.get() };
+        return test_result{ test_status::successful, qemu.exit_code(), buffer.get() };
     }
 
     static test_results run_in_path(const std::filesystem::path test_directory)