fix: fs and util.exec examples do not work on windows (#7193)

docs/by-example/30-reading-writing-files.md

@@ -11,7 +11,7 @@ image: /img/wing-by-example.png
 ```js playground example title="main.w"
 bring fs;
 
-let filename: str = "/tmp/test.txt";
+let filename: str = fs.join(@dirname, "test.txt");
 
 log(fs.exists(filename));
 
@@ -29,6 +29,8 @@ fs.appendFile(filename, "testing");
 let extendedValue = fs.readFile(filename);
 
 log(extendedValue);
+
+fs.remove(filename);
 ```
 
 ```bash title="Wing console output"

docs/by-example/35-exec-processes.md

@@ -11,21 +11,25 @@ image: /img/wing-by-example.png
 ```js playground example title="main.w"
 bring util;
 
-let output = util.exec("echo", ["-n", "Hello, Wing!"]);
+let dir = @dirname;
 
-// exec with custom environment variables
-let output2 = util.exec("bash", ["--norc", "--noprofile", "-c", "echo $WING_TARGET $ENV_VAR"], { env: { ENV_VAR: "Wing" } });
+test "exec()" {
+  let output = util.exec("echo", ["-n", "Hello, Wing!"]);
 
-// exec with inherited environment variables
-let output3 = util.exec("bash", ["--norc", "--noprofile", "-c", "echo $WING_TARGET $ENV_VAR"], { inheritEnv: true });
+  // exec with custom environment variables
+  let output2 = util.exec("bash", ["--norc", "--noprofile", "-c", "echo $WING_TARGET $ENV_VAR"], { env: { ENV_VAR: "Wing" } });
 
-// exec with current working directory
-let output4 = util.exec("bash", ["--norc", "--noprofile", "-c", "echo Hello"], { cwd: "/tmp" });
+  // exec with inherited environment variables
+  let output3 = util.exec("bash", ["--norc", "--noprofile", "-c", "echo $WING_TARGET $ENV_VAR"], { inheritEnv: true });
 
-log(output);
-log(output2);
-log(output3);
-log(output4);
+  // exec with custom working directory
+  let output4 = util.exec("bash", ["--norc", "--noprofile", "-c", "echo Hello"], { cwd: dir });
+
+  log(output);
+  log(output2);
+  log(output3);
+  log(output4);
+}
 ```
 
 ```bash title="Wing console output"