ci: fix tcc compilation of atomic_test.v

vlib/v/gen/c/cheaders.v

@@ -300,6 +300,7 @@ const c_common_macros = '
 #endif
 
 #ifdef __TINYC__
+	#define _Atomic volatile
 	#undef EMPTY_STRUCT_DECLARATION
 	#define EMPTY_STRUCT_DECLARATION voidptr _dummy_pad
 	#undef EMPTY_ARRAY_OF_ELEMS

vlib/v/tests/atomic_test.v

@@ -1,6 +1,3 @@
-import term
-import os
-import runtime
 import time
 
 struct App {
@@ -13,7 +10,7 @@ fn test_atomic() {
 	for i in 0 .. 10 {
 		go app.run()
 	}
-	time.sleep(2 * time.second)
+	time.sleep(200 * time.millisecond)
 	println('idx=$app.idx')
 	assert app.idx == 10
 }