os: add os.write_bytes/2 as a complement to os.read_bytes/1, add test

vlib/os/os.c.v

@@ -62,6 +62,12 @@ pub fn read_bytes(path string) ![]u8 {
 	return res
 }
 
+// write_bytes writes all the `bytes` to `path`.
+@[manualfree]
+pub fn write_bytes(path string, bytes []u8) ! {
+	write_file_array(path, bytes)!
+}
+
 fn find_cfile_size(fp &C.FILE) !int {
 	// NB: Musl's fseek returns -1 for virtual files, while Glibc's fseek returns 0
 	cseek := C.fseek(fp, 0, C.SEEK_END)

vlib/os/os_test.c.v

@@ -784,6 +784,15 @@ fn test_write_file_array_bytes() {
 	// eprintln(rarr.str())
 }
 
+fn test_write_bytes() {
+	fpath := './wbytes.bin'
+	for arr in [[u8(65), 66, 67, 68, 69, 70], [u8(3), 2, 1], []u8{}] {
+		os.write_bytes(fpath, arr)!
+		rarr := os.read_bytes(fpath)!
+		assert arr == rarr
+	}
+}
+
 fn test_write_file_array_structs() {
 	fpath := './astructs.bin'
 	mut arr := []IntPoint{len: maxn}