features: Add support to enable sanitizers

Can be activated/deactivated globally via
WITH_SANITIZE

Can be activated individualy via
WITH_SANITIZE_PORTS

Each port can individually mark itself as not supporting the feature
via SANITIZE_UNSAFE=

Approved by:	bapt, arrowd
Sponsored by:	Netflix
Differential Revision:	https://reviews.freebsd.org/D43497

Mk/Features/sanitize.mk

@@ -0,0 +1,27 @@
+# Sanitize Support
+#
+# Variables that can be used:
+#
+# WITH_SANITIZE		Enable for all ports.
+# 			Sanitizer exits for each bug detected, so it is not
+# 			advisable to enable it globally.
+# WITH_SANITIZE_PORTS	Enable for specified category/port-name
+# SANITIZE_FLAGS	Comma-separated list of sanitizers to be enabled
+# 			Default: address
+#
+
+.if !defined(_SANITIZE_MK_INCLUDED)
+_SANITIZE_MK_INCLUDED=	yes
+SANITIZE_Include_MAINTAINER=	portmgr@FreeBSD.org
+
+.  if !defined(SANITIZE_UNSAFE)
+     SANITIZE_FLAGS?=	address
+.    if defined(_INCLUDE_USES_MESON_MK)
+       MESON_ARGS+= -Db_sanitize=${SANITIZE_FLAGS}
+.    else
+       CFLAGS+=		-fsanitize=${SANITIZE_FLAGS}
+       CXXFLAGS+=	-fsanitize=${SANITIZE_FLAGS}
+       LDFLAGS+=	-fsanitize=${SANITIZE_FLAGS}
+.    endif
+.  endif
+.endif

Mk/bsd.port.mk

@@ -1016,7 +1016,7 @@ LC_ALL=		C
 # These need to be absolute since we don't know how deep in the ports
 # tree we are and thus can't go relative.  They can, of course, be overridden
 # by individual Makefiles or local system make configuration.
-_LIST_OF_WITH_FEATURES=	debug lto ssp pie relro bind_now
+_LIST_OF_WITH_FEATURES=	bind_now debug lto pie relro sanitize ssp
 _DEFAULT_WITH_FEATURES=	ssp
 PORTSDIR?=		/usr/ports
 LOCALBASE?=		/usr/local