parser: fix LTO build

The previous fix for LTO builds in b6d3daa7 did not take into
consideration that LTO support could be added through CFLAGS,in which
case the fix would not be applied.

This patch applied the fix -flto-partition=none even if CFLAGS is
already defined.

Signed-off-by: Georgia Garcia <georgia.garcia@canonical.com>
Closes #214
MR: https://gitlab.com/apparmor/apparmor/-/merge_requests/901
Acked-by: John Johansen <john@jjmx.net>
Merged-by: Georgia Garcia <georgia.garcia@canonical.com>
(cherry picked from commit 0afc2cbb84)

parser/Makefile

@@ -60,7 +60,7 @@ WARNINGS = -Wall
 CXX_WARNINGS = ${WARNINGS} ${EXTRA_WARNINGS}
 CPP_WARNINGS =
 ifndef CFLAGS
-CFLAGS	= -g -O2 -pipe -flto-partition=none
+CFLAGS	= -g -O2 -pipe
 
 ifdef DEBUG
 CFLAGS += -pg -D DEBUG
@@ -70,6 +70,8 @@ CFLAGS = -g -pg -fprofile-arcs -ftest-coverage
 endif
 endif #CFLAGS
 
+CFLAGS	+= -flto-partition=none
+
 EXTRA_CXXFLAGS = ${CFLAGS} ${CPPFLAGS} ${CXX_WARNINGS} -std=gnu++0x
 EXTRA_CFLAGS = ${EXTRA_CXXFLAGS} ${CPP_WARNINGS}