Fix portability of strptime especially for Windows (#3342)

tests/jq.test

@@ -1810,8 +1810,6 @@ try ["OK", bsearch(0)] catch ["KO",.]
 "aa"
 ["KO","string (\"aa\") cannot be searched from"]
 
-# strptime tests are in optional.test
-
 strftime("%Y-%m-%dT%H:%M:%SZ")
 [2015,2,5,23,51,47,4,63]
 "2015-03-05T23:51:47Z"
@@ -1854,6 +1852,20 @@ try ["OK", strflocaltime({})] catch ["KO", .]
 0
 ["KO","strflocaltime/1 requires a string format"]
 
+[strptime("%Y-%m-%dT%H:%M:%SZ")|(.,mktime)]
+"2015-03-05T23:51:47Z"
+[[2015,2,5,23,51,47,4,63],1425599507]
+
+[strptime("%FT%T")|(.,mktime)]
+"2025-06-07T08:09:10"
+[[2025,5,7,8,9,10,6,157],1749283750]
+
+# Check day-of-week and day of year computations
+# (should trip an assert if this fails)
+last(range(365 * 67)|("1970-03-01T01:02:03Z"|strptime("%Y-%m-%dT%H:%M:%SZ")|mktime) + (86400 * .)|strftime("%Y-%m-%dT%H:%M:%SZ")|strptime("%Y-%m-%dT%H:%M:%SZ"))
+null
+[2037,1,11,1,2,3,3,41]
+
 # module system
 import "a" as foo; import "b" as bar; def fooa: foo::a; [fooa, bar::a, bar::b, foo::a]
 null