[master] 5d026a3 Fix ASAN compilation under macaos

[Federico G. Schwindt]

commit 5d026a310b04e6a4a51cadbf69479e7011e98002
Author: Federico G. Schwindt <fgsch at lodoss.net>
Date:   Fri Apr 13 10:49:27 2018 +0100

    Fix ASAN compilation under macaos

diff --git a/configure.ac b/configure.ac
index 48ab568..3877a49 100644
--- a/configure.ac
+++ b/configure.ac
@@ -280,7 +280,11 @@ AC_ARG_ENABLE(msan,
 
 if test "x$UBSAN_FLAGS$TSAN_FLAGS$ASAN_FLAGS$MSAN_FLAGS" != "x"; then
 	SAN_CFLAGS="-D__SANITIZER=1 ${UBSAN_FLAGS} ${TSAN_FLAGS} ${ASAN_FLAGS} ${MSAN_FLAGS} -fPIC -fPIE -fno-omit-frame-pointer"
-	SAN_LDFLAGS="${UBSAN_FLAGS} ${TSAN_FLAGS} ${ASAN_FLAGS} ${MSAN_FLAGS} -pie"
+	SAN_LDFLAGS="${UBSAN_FLAGS} ${TSAN_FLAGS} ${ASAN_FLAGS} ${MSAN_FLAGS}"
+	save_CFLAGS="${CFLAGS}"
+	CFLAGS="${CFLAGS} -Werror=unused-command-line-argument"
+	AX_CHECK_LINK_FLAG([-pie], [SAN_LDFLAGS="${SAN_LDFLAGS} -pie"])
+	CFLAGS="${save_CFLAGS}"
 	case $CC in
 	gcc*)
 		SAN_CFLAGS="${SAN_CFLAGS} -fuse-ld=gold"