Provide a workaround of macos SIP in the build system

[yungyuc]

Mac SIP (System Integrity Protection) was introduced in El Capitan (10.11) in 2015 and it disabled DYLD_*LIBRARY_PATH for some protected binaries (the DYLD_LIBRARY_PATH and DYLD_FALLBACK_LIBRARY_PATH are purged when launching the processes).

make is among the binaries influenced by SIP. Assume that we have a Makefile:

.PHONY:
default:
	@echo "NORMALVAR=$$NORMALVAR"
	@echo "DYLD_LIBRARY_PATH=$$DYLD_LIBRARY_PATH"
	@echo "DYLD_FALLBACK_LIBRARY_PATH=$$DYLD_FALLBACK_LIBRARY_PATH"

and run it by supplying the environment variables. The dyld environment variables are not gone, surprisingly:

$ env NORMALVAR=content DYLD_LIBRARY_PATH=. DYLD_FALLBACK_LIBRARY_PATH=. make
NORMALVAR=content
DYLD_LIBRARY_PATH=
DYLD_FALLBACK_LIBRARY_PATH=

Consequently, we no longer can set the dyld variables outside make and send them to processes spawned in make. A workaround is to use an include file in Makefile. Assume we have a file name setup.mk:

RUNENV ?= DYLD_LIBRARY_PATH=. DYLD_FALLBACK_LIBRARY_PATH=.

The Makefile is modified to:

ifneq (,$(wildcard ./setup.mk))
	include ./setup.mk
endif

.PHONY:
default:
	env $(RUNENV) python3 -c "import os; print(os.environ.get('NORMALVAR'))"
	env $(RUNENV) python3 -c "import os; print(os.environ.get('DYLD_LIBRARY_PATH'))"
	env $(RUNENV) python3 -c "import os; print(os.environ.get('DYLD_FALLBACK_LIBRARY_PATH'))"

python3 is a custom installed Python binary. (If you use the system python, which is a protected binary, this trick won't work.) Running make and the value stored in the include file can be passed to the python3 sub-processes:

$ make
env DYLD_LIBRARY_PATH=. DYLD_FALLBACK_LIBRARY_PATH=. python3 -c "import os; print(os.environ.get('NORMALVAR'))"
None
env DYLD_LIBRARY_PATH=. DYLD_FALLBACK_LIBRARY_PATH=. python3 -c "import os; print(os.environ.get('DYLD_LIBRARY_PATH'))"
.
env DYLD_LIBRARY_PATH=. DYLD_FALLBACK_LIBRARY_PATH=. python3 -c "import os; print(os.environ.get('DYLD_FALLBACK_LIBRARY_PATH'))"
.