package/freerdp: fix build with libexecinfo

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

/home/buildroot/autobuild/instance-0/output-1/host/lib/gcc/riscv64-buildroot-linux-uclibc/10.3.0/../../../../riscv64-buildroot-linux-uclibc/bin/ld: ../../libwinpr/libwinpr2.so.2.5.0: undefined reference to `backtrace_symbols_fd'

Fixes:
 - http://autobuild.buildroot.org/results/095c33098a6e59ff664080e03baf1a3c92b4265f

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

package/freerdp/freerdp.mk

@@ -43,6 +43,11 @@ else
 FREERDP_CONF_OPTS += -DWITH_ALSA=OFF
 endif
 
+ifeq ($(BR2_PACKAGE_LIBEXECINFO),y)
+FREERDP_CONF_OPTS += -DCMAKE_EXE_LINKER_FLAGS=-lexecinfo
+FREERDP_DEPENDENCIES += libexecinfo
+endif
+
 ifeq ($(BR2_PACKAGE_LIBUSB),y)
 FREERDP_CONF_OPTS += -DCHANNEL_URBDRC=ON
 FREERDP_DEPENDENCIES += libusb