partition_table: Check configured flash size fits in partition table

Check happens at build time, so flash size config may need to be changed.

Also fixes MD5_OPT undefined warning, closes https://github.com/espressif/esp-idf/issues/1867

components/partition_table/gen_esp32part.py

@@ -114,6 +114,16 @@ class PartitionTable(list):
                 raise InputError("Partition at 0x%x overlaps 0x%x-0x%x" % (p.offset, last.offset, last.offset+last.size-1))
             last = p
 
+    def flash_size(self):
+        """ Return the size that partitions will occupy in flash
+            (ie the offset the last partition ends at)
+        """
+        try:
+            last = sorted(self, reverse=True)[0]
+        except IndexError:
+            return 0  # empty table!
+        return last.offset + last.size
+
     @classmethod
     def from_binary(cls, b):
         md5 = hashlib.md5();
@@ -350,6 +360,8 @@ def main():
     global md5sum
     parser = argparse.ArgumentParser(description='ESP32 partition table utility')
 
+    parser.add_argument('--flash-size', help='Optional flash size limit, checks partition table fits in flash',
+                        nargs='?', choices=[ '1MB', '2MB', '4MB', '8MB', '16MB' ])
     parser.add_argument('--disable-md5sum', help='Disable md5 checksum for the partition table', default=False, action='store_true')
     parser.add_argument('--verify', '-v', help='Verify partition table fields', default=True, action='store_false')
     parser.add_argument('--quiet', '-q', help="Don't print status messages to stderr", action='store_true')
@@ -377,6 +389,14 @@ def main():
         status("Verifying table...")
         table.verify()
 
+    if args.flash_size:
+        size_mb = int(args.flash_size.replace("MB", ""))
+        size = size_mb * 1024 * 1024  # flash memory uses honest megabytes!
+        table_size = table.flash_size()
+        if size < table_size:
+            raise InputError("Partitions defined in '%s' occupy %.1fMB of flash (%d bytes) which does not fit in configured flash size %dMB. Change the flash size in menuconfig under the 'Serial Flasher Config' menu." %
+                             (args.input.name, table_size / 1024.0 / 1024.0, table_size, size_mb))
+
     if input_is_binary:
         output = table.to_csv()
         with sys.stdout if args.output == '-' else open(args.output, 'w') as f: