MFC r303804:

Fix building usr.bin/tar/tests with PIE symbol building enabled by
removing CFLAGS+= -static

CFLAGS+= -static was a carryover from pre-r289195 with
usr.bin/tar/test/Makefile that should have been specified in LDFLAGS
There doesn't seem to be an apparent need for static compilation
of the test binaries.

Obtained-from: opBSD (418a491eed20d2603ddd1f1bd92c2c0d95094002)