ippool: Fix buildpaths QA error

Pass OE's CFLAGS via CC since the Makefile disregards these flags from
environment and has it own notion of it. This ensures that flags to
rewrite debug flags are passed down correctly to compiler.

Signed-off-by: Khem Raj <raj.khem@gmail.com>

meta-networking/recipes-daemons/ippool/ippool_1.3.bb

@@ -42,7 +42,7 @@ inherit systemd
 DEPENDS = "readline ppp ncurses gzip-native rpcsvc-proto-native libtirpc"
 RDEPENDS:${PN} = "rpcbind"
 
-EXTRA_OEMAKE = "CC='${CC}' AS='${AS}' LD='${LD}' AR='${AR}' NM='${NM}' STRIP='${STRIP}'"
+EXTRA_OEMAKE = "CC='${CC} ${CFLAGS}' AS='${AS}' LD='${LD} ${LDFLAGS}' AR='${AR}' NM='${NM}' STRIP='${STRIP}'"
 EXTRA_OEMAKE += "PPPD_VERSION=${PPPD_VERSION} SYS_LIBDIR=${libdir}"
 # enable self tests
 EXTRA_OEMAKE += "IPPOOL_TEST=y"
@@ -52,12 +52,7 @@ CPPFLAGS += "${SELECTED_OPTIMIZATION} -I${STAGING_INCDIR}/tirpc"
 SYSTEMD_SERVICE:${PN} = "ippool.service"
 
 do_compile:prepend() {
-    # fix the CFLAGS= and CPPFLAGS= in main Makefile, to have the extra CFLAGS in env
-    sed -i -e "s/^CFLAGS=/CFLAGS+=/" ${S}/Makefile
-    sed -i -e "s/^CPPFLAGS=/CPPFLAGS+=/" ${S}/Makefile
-
     sed -i -e "s:-I/usr/include/pppd:-I=/usr/include/pppd:" ${S}/pppd/Makefile
-
 }