mraa: Use -fcommon

gcc10 is going to default to -fno-common which is opposite of all
previous gcc version defaults, ideally package should be fixed so it can
work with -fno-common but this is good enough for now, it does not
change default behavious with older compilers

Signed-off-by: Khem Raj <raj.khem@gmail.com>

meta-oe/recipes-extended/mraa/mraa_git.bb

@@ -27,6 +27,8 @@ EXTRA_OECMAKE_append = " -DINSTALLTOOLS:BOOL=ON -DFIRMATA=ON -DCMAKE_SKIP_RPATH=
                          -DPYTHON_INCLUDE_DIR=${STAGING_INCDIR}/${PYTHON_DIR}${PYTHON_ABI} \
                        "
 
+CFLAGS += "-fcommon"
+
 # Prepend mraa-utils to make sure bindir ends up in there
 PACKAGES =+ "${PN}-utils"