The macro DF is undefined in the MacOS build, resulting in two bogus warnings in the build log.

First warning caused by evaluating "$(shell $(DF) -kP $(OUTPUTDIR) | $(TAIL) -1 | $(NAWK) '{print $$4;}')"

/bin/sh: - : invalid option
Usage: /bin/sh [GNU long option] [option] ...
/bin/sh [GNU long option] [option] script-file ...
GNU long options:
--debug
--debugger
--dump-po-strings
--dump-strings
--help
--init-file
--login
--noediting
--noprofile
--norc
--posix
--protected
--rcfile
--restricted
--verbose
--version
--wordexp
Shell options:
-irsD or -c command or -O shopt_option (invocation only)
-abefhkmnptuvxBCHP or -o option


FREE_SPACE has no value due to the first warning.

Second warning is caused by evaluating "@if [ -d $(OUTPUTDIR) -a $(FREE_SPACE) -lt $(MIN_FREE_DISK) ]; then"

/bin/sh: line 0: [: too many arguments



Both are generated by the free disk space checking in install/make/common/Sanity.gmk: