Add 2020/endoh3/run_clock.alt.sh for alt code

The alt code provided by the author back in 2020 uses Unicode but there
wasn't a script for it (the script run_clock.sh which I made some fixes
in last year was added by the judges but no version for the alt code was
added).

The scripts also have another fix in them: make clock or make clock.alt
first as if not and the program does not exist the script will happily
overwrite the C files and prevent it from being compiled. They use 'make
-B' just to be sure that it's compiled.

2020/endoh3/.gitignore

@@ -1,6 +1,8 @@
 #
 # sort with: sort -d -u
 clock
+clock.alt
+clock.alt.c
 clock.c
 *.dSYM
 indent