Try the ssreflect apply at the place the CI builder fails.

I cannot reproduce the error of the CI builder on my machine with the
same version of Coq (8.5pl2).
1 job for master in 3 minutes and 6 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
failed #607
coq
buildjob

00:03:06

 
Name Stage Failure
failed
buildjob Test There is an unknown failure, please try again
Makefile.coq:384: recipe for target 'program_logic/adequacy.vo' failed
make[1]: *** [program_logic/adequacy.vo] Error 1
make[1]: *** Waiting for unfinished jobs....
program_logic/ectx_lifting (user: 4.83 mem: 495624 ko)
program_logic/boxes (user: 22.53 mem: 546308 ko)
make[1]: Leaving directory '/builds/FP/iris-coq'
Makefile:7: recipe for target 'all' failed
make: *** [all] Error 2
ERROR: Build failed: exit code 1