package/connman: fix build with libexecinfo

Fix the following build failure raised on uclibc and musl since the
addition of libexecinfo package in commit
eea8ba446c10701a273432552108d80fb2224ef4:

/home/peko/autobuild/instance-0/output-1/host/opt/ext-toolchain/bin/../lib/gcc/x86_64-buildroot-linux-uclibc/10.3.0/../../../../x86_64-buildroot-linux-uclibc/bin/ld: src/backtrace.o: in function `print_backtrace':
backtrace.c:(.text+0x37): undefined reference to `backtrace'

Fixes:
 - http://autobuild.buildroot.org/results/74da4f4deab5f0ae9405d063ad52a5d4904a964d

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/connman/connman.mk

@@ -109,4 +109,9 @@ else
 CONNMAN_CONF_OPTS += --disable-client
 endif
 
+ifeq ($(BR2_PACKAGE_LIBEXECINFO),y)
+CONNMAN_DEPENDENCIES += libexecinfo
+CONNMAN_CONF_ENV += LDFLAGS="$(TARGET_LDFLAGS) -lexecinfo"
+endif
+
 $(eval $(autotools-package))