Remove unused DBUG_EXECUTE_IF "ignore_punch_hole"

Since commit ea21d630 we
conditionally define a variable that only plays a role on
systems that support hole-punching (explicit creation of sparse files).
However, that broke debug builds on such systems.

It turns out that the debug_dbug label "ignore_punch_hole" is
not at all used in MariaDB server. It would be covered by
the MySQL 5.7 test innodb.table_compress. (Note: MariaDB 10.1
implemented page_compressed tables before something comparable
appeared in MySQL 5.7.)

storage/innobase/buf/buf0flu.cc

@@ -945,10 +945,6 @@ static bool buf_flush_page(buf_page_t *bpage, bool lru, fil_space_t *space)
 #if defined HAVE_FALLOC_PUNCH_HOLE_AND_KEEP_SIZE || defined _WIN32
       if (size != orig_size && space->punch_hole)
         type= lru ? IORequest::PUNCH_LRU : IORequest::PUNCH;
-#else
-      DBUG_EXECUTE_IF("ignore_punch_hole",
-                      if (size != orig_size && space->punch_hole)
-                        type= lru ? IORequest::PUNCH_LRU : IORequest::PUNCH;);
 #endif
       frame=page;
     }

storage/innobase/os/os0file.cc

@@ -3538,13 +3538,6 @@ os_file_set_nocache(
 @return true if the file system supports sparse files */
 IF_WIN(static,) bool os_is_sparse_file_supported(os_file_t fh)
 {
-	/* In this debugging mode, we act as if punch hole is supported,
-	then we skip any calls to actually punch a hole.  In this way,
-	Transparent Page Compression is still being tested. */
-	DBUG_EXECUTE_IF("ignore_punch_hole",
-		return(true);
-	);
-
 #ifdef _WIN32
 	FILE_ATTRIBUTE_TAG_INFO info;
 	if (GetFileInformationByHandleEx(fh, FileAttributeTagInfo,
@@ -3795,13 +3788,6 @@ os_file_punch_hole(
 @return DB_SUCCESS or error code */
 dberr_t IORequest::punch_hole(os_offset_t off, ulint len) const
 {
-	/* In this debugging mode, we act as if punch hole is supported,
-	and then skip any calls to actually punch a hole here.
-	In this way, Transparent Page Compression is still being tested. */
-	DBUG_EXECUTE_IF("ignore_punch_hole",
-		return(DB_SUCCESS);
-	);
-
 	ulint trim_len = bpage ? bpage->physical_size() - len : 0;
 
 	if (trim_len == 0) {