package/exim: fix build with libexecinfo

Upstream added optional support for execinfo

https://git.exim.org/exim.git/commitdiff/204a7a2c2e8601558905dc34c576a627045a9f21
https://git.exim.org/exim.git/commitdiff/48ea675fee2d5fee8d33c525e28727b69114cfce

in version 4.97 which was added to buildroot with commit
faec3ca30e358575f70a036879029f63f7da9b29

Fixes:
http://autobuild.buildroot.net/results/282/282882371e1d8c224c457bf65016f8abd11f8c45/

Signed-off-by: Bernd Kuhls <bernd@kuhls.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
(cherry picked from commit 22b629729667bac6aa3a9c5079be4487bb850d23)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/exim/exim.mk

@@ -103,6 +103,7 @@ define EXIM_CONFIGURE_TOOLCHAIN
 	$(call exim-config-add,RANLIB,$(TARGET_RANLIB))
 	$(call exim-config-add,HOSTCC,$(HOSTCC))
 	$(call exim-config-add,HOSTCFLAGS,$(HOSTCFLAGS))
+	$(call exim-config-add,EXTRALIBS,$(EXIM_EXTRALIBS))
 	$(EXIM_FIX_IP_OPTIONS_FOR_MUSL)
 endef
 
@@ -126,6 +127,13 @@ ifeq ($(BR2_STATIC_LIBS),y)
 EXIM_STATIC_FLAGS = LFLAGS="-pthread --static"
 endif
 
+ifeq ($(BR2_PACKAGE_LIBEXECINFO),y)
+EXIM_DEPENDENCIES += libexecinfo
+EXIM_EXTRALIBS += -lexecinfo
+else ifeq ($(BR2_TOOLCHAIN_USES_GLIBC),)
+EXIM_CFLAGS = -DNO_EXECINFO
+endif
+
 # We need the host version of macro_predef during the build, before
 # building it we need to prepare the makefile.
 define EXIM_BUILD_CMDS
@@ -136,7 +144,7 @@ define EXIM_BUILD_CMDS
 		CFLAGS="-std=c99 $(HOST_CFLAGS)" \
 		LFLAGS="-fPIC $(HOST_LDFLAGS)"
 	$(TARGET_MAKE_ENV) build=br $(MAKE) -C $(@D) $(EXIM_STATIC_FLAGS) \
-		CFLAGS="-std=c99 $(TARGET_CFLAGS)"
+		CFLAGS="-std=c99 $(TARGET_CFLAGS) $(EXIM_CFLAGS)"
 endef
 
 # Need to replicate the LFLAGS in install, as exim still wants to build