fix(docker): tweak makefile to fetch updated requirements

Tweak the makefile so we check the modification time of the parent
requirements.txt before we continue with the current one. This only
affects people building this locally, as CI always starts with a fresh
copy.

Signed-off-by: Randolph Sapp <[email protected]>

Author: StaticRocket

docker/Makefile

@@ -19,5 +19,5 @@ all: Dockerfile setup
 
 setup: requirements.txt
 
-requirements.txt:
+requirements.txt: ../requirements.txt
 	cp -ar ../requirements.txt .