flex: use persistent SRCURL

preventing github getting drowned in amazon
```
[BEE] fetching https://github.com/westes/flex/releases/download/v2.6.4/flex-2.6.4.tar.gz
--2020-09-15 19:08:30--  https://github.com/westes/flex/releases/download/v2.6.4/flex-2.6.4.tar.gz
Location: https://github-production-release-asset-2e65be.s3.amazonaws.com/14521001/23794388-327c-11e7-8219-c41432b94acf?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIAIWNJYAX4CSVEH53A%2F20200915%2Fus-east-1%2Fs3%2Faws4_request&X-Amz-Date=20200915T170830Z&X-Amz-Expires=300&X-Amz-Signature=aefed42a6b555e6063cc316d235473be654bb102689df4bb9daf2374967b2b2b&X-Amz-SignedHeaders=host&actor_id=0&key_id=0&repo_id=14521001&response-content-disposition=attachment%3B%20filename%3Dflex-2.6.4.tar.gz&response-content-type=application%2Foctet-stream [following]
[...]
   700K .......... .......... .......... .......... .......... 54% 8.80K 76s
   750K .......... .......... .......... .......... .......... 57% 1.88K 85s
   800K .......... .....                                       58% 68.8K=1m56s

2020-09-15 19:11:30 (7.03 KB/s) - Read error at byte 835148/1419096 (Success.). Giving up.

```

flex.be0

@@ -1,13 +1,14 @@
 #!/usr/bin/env beesh
 
-# BEE_VERSION flex-2.6.4-0
+# BEE_VERSION flex-2.6.4-1
 
 # more info: https://github.com/westes/flex
 # https://www.archlinux.org/packages/core/x86_64/flex/
 
-SRCURL[0]="https://github.com/westes/flex/releases/download/v${PKGVERSION}/flex-${PKGVERSION}.tar.gz"
+# SRCURL[0]="https://github.com/westes/flex/releases/download/v${PKGVERSION}/flex-${PKGVERSION}.tar.gz"
+SRCURL[0]="https://beehive.molgen.mpg.de/2882e3179748cc9f9c23ec593d6adc8d/flex-2.6.4.tar.gz"
 
-PATCHURL+=( /src/mariux/md5repo/0a8e8242b37c57b0bc0c6f673bceb5b7/flex-pie.patch )
+PATCHURL+=( "https://beehive.molgen.mpg.de/0a8e8242b37c57b0bc0c6f673bceb5b7/flex-pie.patch" )
 
 # build_in_sourcedir