Enable position independent executable.

sapwmp.x86_64: E: non-position-independent-executable
               (Badness: 10000) /usr/lib/sapwmp/sapwmp-capture
This executable must be position independent.  Check that it is
built with -fPIE/-fpie in compiler flags and -pie in linker flags.

configure.ac

@@ -4,6 +4,9 @@ AC_PROG_CC
 AC_PROG_CC_C99
 AC_CONFIG_FILES(Makefile)
 
+AC_SUBST([CFLAGS], [-fPIE])
+AC_SUBST([LDFLAGS], [-pie])
+
 PKG_CHECK_MODULES(LIBSYSTEMD, [libsystemd])
 
 AC_OUTPUT