[Makefile] Run `pip uninstall` before `pip install`.
This is to reduce the risk of a pip-installed version of CompilerGym
from co-existing with the version installed by `make install`. This can
lead to the incorrect version being used and cryptic errors, for example
see
@@ -354,7 +354,10 @@ post-install-test:
# Installation #
################
-pip-install:
+# We run uninstall as a dependency of install to prevent conflicting
+# CompilerGym versions co-existing in the same Python environment.
+
+pip-install: uninstall
$(PYTHON) setup.py install
install: | init-runtime-requirements bazel-build pip-install
