lang/gcc10: fix runtime on powerpc64le

It looks like this part was omitted during upstreaming.
Its lack causes gcc to be compiled successfully, but fail at building simple programs:
/usr/local/bin/ld: /usr/local/lib/gcc10/libgcc_s.so: undefined reference to `.udivmodti4'
/usr/local/bin/ld: /usr/local/lib/gcc10/libgcc_s.so: undefined reference to `.ctzdi2'
/usr/local/bin/ld: /usr/local/lib/gcc10/libgcc_s.so: undefined reference to `.parityti2'
/usr/local/bin/ld: /usr/local/lib/gcc10/libgcc_s.so: undefined reference to `.enable_execute_stack'