remove no-longer-needed Makefile hackery

2 jobs for master in 17 minutes and 19 seconds (queued for 25 minutes and 31 seconds)
Status Job ID Name Coverage
  Build
failed #19965
fp
build-coq.8.6.1

00:15:01

passed #19964
fp
build-coq.8.7.2

00:14:51

 
Name Stage Failure
failed
build-coq.8.6.1 Build
COQC theories/examples/symbol.v
make[1]: Target 'all' not remade because of errors.
Makefile:6: recipe for target 'all' failed
make: *** [all] Error 2

real 5m4.893s
user 12m11.388s
sys 0m20.200s
ERROR: Job failed: exit code 1