gdbc6x: suppress gcc10 multiple definitions of *_varobj_ops

Workaround for the following gcc10 errors:
.../gdbc6x/gdb/varobj.h:221: multiple definition of `ada_varobj_ops'; mi-cmd-var.o:.../gdbc6x/gdb/./varobj.h:221: first defined here
.../gdbc6x/gdb/varobj.h:220: multiple definition of `java_varobj_ops'; mi-cmd-var.o:.../gdbc6x/gdb/./varobj.h:220: first defined here
.../gdbc6x/gdb/varobj.h:219: multiple definition of `cplus_varobj_ops'; mi-cmd-var.o:.../gdbc6x/gdb/./varobj.h:219: first defined here
.../gdbc6x/gdb/varobj.h:218: multiple definition of `c_varobj_ops'; mi-cmd-var.o:.../gdbc6x/gdb/./varobj.h:218: first defined here

Needs to be resolved properly in the code later:
https://gcc.gnu.org/gcc-10/porting_to.html

Signed-off-by: Denys Dmytriyenko <denys@konsulko.com>

recipes-devtools/gdbc6x/gdbc6x_git.bb

@@ -19,6 +19,8 @@ S = "${WORKDIR}/git/gdbc6x"
 inherit update-rc.d
 inherit gettext
 
+CFLAGS += "-fcommon"
+
 do_configure () {
     cd ${S}
     ./configure --program-suffix=c6x --target=tic6x-elf-tirtos --host=${HOST_SYS} --prefix=${S}/install_gdb