Fixed breakage of POSIX support in rev.1.31. -pipe was added to

CFLAGS in all cases, but POSIX requires a default of -O.  Adding
-pipe unconditionally still is still broken for non-gcc compilers
in the non-POSIX case.

share/mk/sys.mk

@@ -34,10 +34,11 @@ AFLAGS		?=
 
 .if defined(%POSIX)
 CC		?=	c89
+CFLAGS		?=	-O
 .else
 CC		?=	cc
-.endif
 CFLAGS		?=	-O -pipe
+.endif
 
 CXX		?=	c++
 CXXFLAGS	?=	${CFLAGS:N-std=*}