[PBCKP-245] mingw: ucrt strftime is good enough

msvcrt's strftime is quite limited, and we had to use pg_strftime.

On the other hand, ucrt's one is capable for most of SU (Single UNIX)
extensions, so we could safely use it.

That means, we restrict windows port to MinGW64 UCRT environment.

Author: funny-falcon

src/pg_probackup.h

@@ -43,6 +43,10 @@
 
 #include "pg_probackup_state.h"
 
+#if defined(WIN32) && !(defined(_UCRT) && defined(__MINGW64__))
+#error Windows port requires compilation in MinGW64 UCRT environment
+#endif
+
 /* Wrap the code that we're going to delete after refactoring in this define*/
 #define REFACTORE_ME
 

src/utils/logger.c

@@ -811,11 +811,7 @@ logfile_getname(const char *format, time_t timestamp)
 	len = strlen(filename);
 
 	/* Treat log_filename as a strftime pattern */
-#ifdef WIN32
-	if (pg_strftime(filename + len, MAXPGPATH - len, format, tm) <= 0)
-#else
 	if (strftime(filename + len, MAXPGPATH - len, format, tm) <= 0)
-#endif
 		elog_stderr(ERROR, "strftime(%s) failed: %s", format, strerror(errno));
 
 	return filename;