os: improve robustness of create_folder_when_it_does_not_exist/1 (fix CI false positives for vab-compiles-v-examples) (#22548)

Author: spytheman

vlib/os/os.v

@@ -800,15 +800,27 @@ fn create_folder_when_it_does_not_exist(path string) {
 	if is_dir(path) || is_link(path) {
 		return
 	}
-	mkdir_all(path, mode: 0o700) or {
-		if is_dir(path) || is_link(path) {
-			// A race had been won, and the `path` folder had been created,
-			// by another concurrent V executable, since the folder now exists,
-			// but it did not right before ... we will just use it too.
-			return
+	mut error_msg := ''
+	for _ in 0 .. 10 {
+		mkdir_all(path, mode: 0o700) or {
+			if is_dir(path) || is_link(path) {
+				// A race had been won, and the `path` folder had been created, by another concurrent V program.
+				// We are fine with that, since the folder now exists, even though this process did not create it.
+				// We can just use it too  ¯\_(ツ)_/¯ .
+				return
+			}
+			error_msg = err.msg()
+			sleep_ms(1) // wait a bit, before a retry, to let the other process finish its folder creation
+			continue
 		}
-		panic(err)
+		break
+	}
+	if is_dir(path) || is_link(path) {
+		return
 	}
+	// There was something wrong, that could not be solved, by just retrying
+	// There is no choice, but to report it back :-\
+	panic(error_msg)
 }
 
 fn xdg_home_folder(ename string, lpath string) string {

vlib/os/sleeping.c.v

@@ -0,0 +1,26 @@
+module os
+
+pub struct C.timespec {
+pub mut:
+	tv_sec  i64
+	tv_nsec i64
+}
+
+fn C.nanosleep(req &C.timespec, rem &C.timespec) int
+
+// sleep_ms provides a cross platform way to sleep, without having to `import time` for a time.sleep/1 call.
+fn sleep_ms(ms i64) {
+	$if windows {
+		C.Sleep(u32(ms))
+	} $else {
+		mut req := C.timespec{ms / 1000, 1_000_000 * (ms % 1000)}
+		rem := C.timespec{}
+		for C.nanosleep(&req, &rem) < 0 {
+			if C.errno == C.EINTR {
+				req = rem
+			} else {
+				break
+			}
+		}
+	}
+}

vlib/os/sleeping.js.v

@@ -0,0 +1,8 @@
+module os
+
+// sleep_ms suspends the execution for a given duration (in milliseconds), without having to `import time` for a single time.sleep/1 call.
+fn sleep_ms(dur i64) {
+	#let now = new Date().getTime()
+	#let toWait = BigInt(dur)
+	#while (new Date().getTime() < now + Number(toWait)) {}
+}