libsepol/Makefile: add -fno-semantic-interposition

Add -fno-semantic-interposition to CFLAGS. This will restore
the DSO infrastructures protections to insure internal callers
of exported symbols call into libselinux and not something loading first
in the library list.

Clang has this enabled by default.

Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: William Roberts <william.c.roberts@intel.com>

libsepol/src/Makefile

@@ -19,7 +19,7 @@ LIBMAP=libsepol.map
 LIBSO=$(TARGET).$(LIBVERSION)
 OBJS= $(patsubst %.c,%.o,$(sort $(wildcard *.c)))
 LOBJS= $(patsubst %.c,%.lo,$(sort $(wildcard *.c)))
-CFLAGS ?= -Werror -Wall -W -Wundef -Wshadow -Wmissing-format-attribute -O2
+CFLAGS ?= -Werror -Wall -W -Wundef -Wshadow -Wmissing-format-attribute -O2 -fno-semantic-interposition
 
 override CFLAGS += -I. -I../include -D_GNU_SOURCE